It's pretty common to not feel like you're doing a great job at work (or in your projects, or whatever else). I know I tend to definitely remember negative things that folks say to me or times that I feel like I have messed up.
We don't remember the positive things, generally speaking. I have a simple technique to help with this. Whenever someone shares (either privately or publicly) an accolade, I save it into a private notebook.
I first came up with this idea when I was a newly minted sales engineer at Chef. I was super nervous and felt like I wasn't accomplishing anything. Then, I got the following message from a coworker of mine that I really looked up to:
This made a massive difference to me in the moment, but the fact that whenever I am feeling like I am "not good enough", I can always go back to my "compliments" notebook. It's very telling that even today, over six years later, that one comment from Chip still has the power to make me re-center my self-belief.
Any time that I am feeling "less than", or that I don't belong, or that I am not valuable, a simple review of my "compliments" notebook often helps.
This has an additional use as well - when it comes time for annual review, go back through this notebook! It will help you remember the things you did to help your colleagues and community members.
 - I used to use Evernote for this, but you can use whatever works for you! Even a simple Google Doc that you just paste things into is fine! Don't overthink it!