I become discouraged when a girl I like has another male around.

For some reason, whenever I have a crush, or a girl I like, just seeing her have a guy friend, or be talking to a guy, or even hugging him I always get extremely discouraged and decide it’s not worth it. I guess I know why, but I don’t. Maybe it’s because I see other males in their life as having greater potential than me, and I assume she already likes them so there’s no point in trying. I don’t know how to fix this