I think this is a question I had too early on in my career and I think I am near an answer. See if this can help you.
Everyday when I wake up in the morning, I want to outdo myself and be the best engineer I can be. But, deep deep down, how do I know if I'm actually good enough? Sure, I ship features, fix bugs and brainstorm ideas. But, what's a good measure of how good you're?
I think self evaluation is a very very important thing to do, not just in programming but in any field of work. Also, it's important to keep learning. The problems begin when you stop learning.
I think once you work on a big feature and it works as expected and holds up at scale, you feel a sense of achievement and pride. I mean, you made this thing work and designed it. How cool is that?
Long story short, sit down and make a list of all the features you've shipped. You made those things, not anybody else. Also, you got to whatever place you're in because of the all work you've put in over the years. You did it on your own. That's a huge deal and something you must take a lot of pride in.