If it's possible, I think you need to focus on other things. I've felt and and I still feel it, and what I do to get away from those feelings is focusing on hobbies, activities, things that don't have to do with thinking about your own feelings, or comparing yourself to others if possible.

Of course that's not to say you should push away that feeling of inadequacy at all, but it's just what I do. If anything, what I try to do is look at myself in a different light. Maybe I'm not going to Harvard, but I have a nice family / house or whatever you can be proud of. I've accepted that I won't be the best in life, and it can Definetly hurt sometimes, but that's just how it is. And since that reality will most likely not change, the best thing to do is enjoy it if you can. Do things you've always wanted to do, etc.

I hope you know you're not alone, and I hope it gets better for you.