I'm sick of people telling me I can do better!! What to do!?

Im 19 years old, and my friends are really getting to me. Everytime I meet someone that I'm attracted to and have feelings for, they rain on my parade and tell me he's ugly, that I'm "too good" for him etc. It just drives me crazy! No one is too good for anyone and if I like them, y must they tarnish my happiness? I'd never do it to them. It makes me feel very awkward and I hate that they think someone I like is not good enough, and I don't know what to do about this.