I had always for the most attributed this "'I'm not good enough" belief to being teased as a kid, having little experience with women and having limited social skills - But I was in the gym this morning and this ed sheeran song 'perfect' came on and it was essentially about how this chick he's with is perfect and that he doesn't deserve her blah blah blah... And it made me realize how many different movies, tv shows, songs and/or whatever push this idea into our minds - Essentially that you are not good enough, that she's too perfect for you and that you don't deserve her - It's complete bullshit because the guys writing and believing this are basing this belief solely on her physical appearance and literally nothing else, it's pretty cringe if you think about it.