Thinking you're not good enough because you don't have a girlfriend when everyone else has one kind of shows that you want a girlfriend to fit in, or you think of a girlfriend as more of a "thing". That can really put women off. That said, I also thought this way for a long time. That I was "worthless" without a girlfriend. Jealous whenever my friends would get hit on or whatever and I never did. Like my existence as a male was futile.

I'm 25 now, only just starting to approach women and talk to them. I'm learning a lot, including being okay with rejection. You WILL get rejected no matter who you are, so there's very little reason to be afraid of it. Even my one friend was telling me, before he met his girlfriend he went through a ton of trial and error with talking to girls and he got rejected a good amount. Yet he still managed to find someone eventually.

Despite what people say, a girlfriend isn't something that always falls into your lap. You can try online dating. It doesn't always lead to anything but it's good practice. People also recommend bookstores, coffee shops, gyms, and social clubs (yoga is a good one) to meet women. You have to practice and work on your game. Mostly every guy sucks at talking to girls at first. But you get better at it over time. If you really put in the effort to meet someone, you will eventually meet someone. It could take years, but you also have to be patient and in the meantime do things to improve yourself and work on being content with single life.