I find that I often do better with big cubes in competition than with small cubes, because with big cubes I tend to eventually settle down and relax, since it takes so long. Competitions that begin with 6x6x6 or 7x7x7 tend to be good speedsolving competitions for me (like the most recent one I attended, where I got 6 PBs!).
This is something I struggled with a lot for a year or two. I agree with Mike, longer events like 5x5 or megaminx allow me to just settle into the solve.
That is really interesting about big cubes and it allowing you to settle in, but it makes a lot of sense and I do agree with it. Thank you for that.
I do often do worse in competitions I'm running - distractions from making sure the competition is running smoothly tend to make it harder to focus on the cubing. I understand you tend to help out a lot at the competitions you attend (and even ran one?); I don't want to discourage that - I think it's great, and I really hope you will continue to do so. But perhaps even just making sure you take a few minutes to think calm thoughts before you begin a round might help. Some people here have talked about using meditation techniques or slow breathing to calm themselves before solving; I've had some luck with that sort of thing.
That is exactly one of the things that I thought about after the competition and something that I was told by some family and friends (but you explained it better...of course

). I have hosted my own comp as well as staffed at every competition that I have been to (For better or worse) and I really enjoy being able to help out and keep the competition running, that I do forget to (like you said) spend a few minutes focusing on the event I am about to do, and thus not being prepared for the solves. This is something that I am going to work on for all future competitions, and thank you very much for the advice.
I have also been looking/watching a few videos on breathing because that is something that I struggle with (in anything) especially when I am nervous, my heart is beating 100mph and I need to work on relaxing, because for me when my heart is beating really fast, I have a hard time preforming right and that is something that I will really work on as well. So again than you for mentioning that, it is something that I needed to hear and work on, among a lot of other stuff.
I also got another bit of advice recently from one of Kevin Hays' livestream videos. He said, you have to find a turning style that works for you in comps, that may be different from what you use at home. This may be because you are a little more shaky in comps, so you need to be a little slower and smoother, but may even be able to adapt this to be almost as fast as before. Think about the classic advice for improving lookahead- slow down the turn speed until you can track your next move and never have to pause. Then you can gradually speed up until you reach your previous speed but with no pauses. Think of your competition turning style as being somewhere along that spectrum. Focus on purposely being slower than your at-home turning speed in order to help your lookahead. The first few times you try this, commit to the fact that you will not get close to your at-home speed. But you will get much closer than you have previously, which will hopefully in turn lower your nervousness to allow you to improve the next time.
EDIT: Pick the right cube, as well. If you are shaky in comps, DO NOT use a floppy cube, even if it might be better for you at home. For example, rewind to around 2015 when I tried to use my GAN356 in comp. That was a bad idea and I quickly went back to the mini Weilong. Fast forward to now, and my at-home main is a Valk3 but my comp main is my Thunderclap V1 M...
That is really great advice and something that I was thinking about the other day, when I was thinking back on the competition. I realized that in a few events (especially 5x5) where although it is the only white plastic cube I have as my main, I can have great look ahead at home with it, but at the competition I spent most of my time pausing and looking for edges pieces to pair up, and I think that it has something to do with the plastic color because in competitions I noticed that I was doing better with stickerless cubes and black plastic, but when I tried someone else white plastic I had a harder time looking ahead. I am going to try different cubes for my next competition and see which ones I preform better with. I also really like my cubes to be faster (at home) but I think that if for now I have a slightly slower cube (or at least slow down my TPS and or change my main) then I will do much better. Something that I did have harder times with was not locking up/catching a the competition, which almost never happens at home for me, but it is something that I really need to work on at competitions. Thanks for the advice.
Kind of a long rambling reply, but hopefully there's something in there that helps you out.
Keep rambling on

All of what you and everyone else has said is helping a ton, and I do sincerely appreciate all of you taking the time to provide advice and help.
Personally, one thing I found weird was using a stackmat while solving, something I had not practiced at home.
That is interesting. I have almost always used a stackmat at home, and with in these last several months it is the only thing that I have been using. So for me being comfortable with a stackamt was not a issue, but I do completely understand what you are saying and thank you for mentioning it.
Along with this and nerves, I would get averages that were 2-4 seconds slower than what I was used to. To calm my nerves, I always have another cube with me next to the table. When my judge asks if I'm ready, I take a couple deep breaths, do a couple really slow algs on my cube, and just keep repeating it until I feel ready. It's kinda like having a set motion to calm yourself before a freethrow in basketball. Find something that works for you, and just repeat it over and over again until you're calm and can focus on your solve.
Perfect advice. To be honest I have never really done that at any competition and although I will have cube with me most of the time, I only have really used with off and on while I am in the waiting area, but yet for right before my solve, so thank you very much for the advice, and it is again something that I will really work on for/at my next competition.
I really didn't care at all about big cubes, and always got really good results in them.
I've PBed my 7x7 single twice in competition, my first sub 5 and third sub 5. I cannot express how little I care about 7x7, or how much that helps me get fast times (for me).
What eventually solved it for me was I finally went to a comp and was able to trick myself into not caring about the solves. I just figured, here's my cube, I'll solve it, whatever. I ended up getting a pretty good average over the course of the day, and the next comp I went to, all that pressure was off. I didn't have to worry about having to pb because I already had a good average. Maybe that isn't very applicable to you, but I think the key for me was that one decision, when I went in and just said, whatever.
Great advice from both of you, and again something that I really needed to hear/work on. I think that for me I want to do a lot better in all the events that I think about them to much and the possible outcome and times that I do not focus on the solve and look ahead as I should. I realized that especially after I got a 5x5 BLD success, and what I mean is, throughout the whole competition I was really hoping to qualify for events before Nationals and also get SR in several events that I in did up thinking messing up on the solves rather then focus on the solve, and the only event that I did not think I would get a success/even care about because I was really disappointed with all the other results and did not think a success would happen was 5x5 BLD. So after the I realized that needed to do that for all the other events at my next competition. SO again thank you for that advice.
Also, have you tried cubing with friends or family specifically and deliberately watching you? You could go to a park and just do some solves outside where strangers would see you and probably watch. That might help you get used to solving around people.
This is something that I am going to really try and do a lot more of, especially in regards to cubing around strangers and in public. I can get good times around my family (mainly because the room that I cube in is one of the main family rooms in our house) and so I constantly have someone watching me, so for me I am pretty used to that, but not cubing in public, which is something that I hope to do a lot more of soon.
Thank you all very much for all the help and advice that you have all given. I do sincerely appreciate you taking the time to help me and others out with all of this.
Edit: Sorry for spelling "Several" wrong in the poll question. I can not seem to edit it, but if you have any tips on that, that would be great. Thanks