Undertake something that is difficult; it will do you good. Unless you try to do something beyond what you have already mastered, you will never grow. ~~ Ronald E. OsbornI don't know if you're prone to it, but I fall back on tasks that come easily and must force myself to accept the challenge of the difficult. I guess that's human nature, but I know my writing will always be much better if I stretch to my limits.
Have you looked back on pieces you wrote ten years ago. You should be able to notice quite a difference. The growth in your writing should show. If it doesn't, you may not be undertaking the difficult. Challenge yourself... grow.