Well, I have heard that before and I know. The question was how to get better f2l? My average is about 21 sec, an it doesn't seem to be much better.
Your F2L is 21 seconds?
or your whole solve is 21 seconds?
If its 21 seconds for F2L, I get around that also and average 27 seconds.
And I can't seem to get better, well at least I think, but I know I am, I'm learning new cases every day.
If you whole solve is 21 seconds, then I don't know what to tell you, i'm not quite there yet >.<