Improve the quality of problems you are capable of solving.

Growth shows up less in solving the same problems faster and more in the class of problem you can take on at all. What was once beyond you becomes merely difficult, and difficult becomes routine. That upward shift is the real measure, and it is easy to miss because each new level feels just as hard as the last.

Look at what you are struggling with now and compare it to what you struggled with three years ago. If they are the same problems, the struggle is a plateau rather than a climb.