I have found that recognizing my own changes and accomplishments help me feel better and more confident about myself. It's often hard to see those changes if they are happening slowly. My partner helped me see them when I was "too close" to the situation. I've though about journaling about my accomplishments and seeing how those change over time
I also think we see our flaws a lot more harshly than other people do. Also when we compare ourselves to others we are only comparing against what we see of others - there is so much of how others actually live their lives that we dont know of
For example, a friend of mine in a group chat was quiet all week and didn't respond to many messages. Based on her social media I could assume she was off having a great time doing things I wish I was doing and too busy to talk to me. But it turned out she was having a really bad week with anxiety attacks. So that changed my perspective on this friend whose life looks really great from what I see of it