I have experienced, and still continue to, experience this in my academic work. I feel quite embarrassed about many of my early papers. How shallow they were! How utterly lacking in novelty, in significance, in rigor! But over time measured in years, I found, at first to my surprise, that the quality of the papers I am working on is growing, slowly but steadily. This gives me confidence that I'm improving, and feeds the hope that I may yet meet at least my own standards some day (though they are also creeping up in their own sneaky way).
Here is a poster version of the same piece that has been circulating around the web (please tell me if you know who to credit for this):