If you really want to see proof of your improvement as a writer, look over the stuff you wrote as a student.
We recently moved, and during our pre- and post-move decluttering, I stumbled onto a milk crate filled with my old college English Lit papers.
Re-reading them was a horrifying experience. Horrifying. I was shocked to see my muddled mind, my flowery sentences and my affected writing style. It was embarrassing to see how hard I tried to please my professors. It literally hurt my eyes to read these papers.
Ironically, my grades were all A's and B's, which makes me shudder all the more.
Now, fortunately, my writing is far more cogent and lucid. I don't reach quite so often for big words, and when choosing between flowery phrasing and something stripped-down and simple, I'm confident enough now to choose the latter.
Read your old stuff. You'll feel grateful when you see how far you've come.