I remember a time in my career when I looked at some code and I was truly impressed by whoever had written it. It was different from the code I was used to finding in the company's codebase. The intent was clear, it was efficient, etc. I looked into the source code history to see who wrote it. I was surprised to find that I had written it, but I'd entirely forgotten writing it. I got a good laugh out of that... but I was mildly disappointed that I couldn't praise someone else.

Of course this is the exception rather than the rule. I've done a lot of revision on my code. If you don't look back on your code and think of ways it can improve then there's a good chance you're not learning.