I have a theory that as your body and mind grows, your overall ability to solve the cube grows too.
That's why you'll get better after a long pause or by just practicing something that doens't have a direct connection to cubing.
I remember coming back to megaminx after a really long pause and being able to understand the overall theory of block building a lot better than in the past.
Sometimes we must just let our mind and body to grow and not force our organism into doing something we can't at the moment.