Debby Downers -.-

No matter what you do there's always going to be a Debby Downer....I have social anxiety and I'm 17 and trying to grow up but how.....when I'm always excited about something or happy there ALWAYS seems to be someone who downs it or ruins it.....how do I cope with this? What people say to and about me really gets to me even if it's something little and it bothers me I get bothered by something stupid.....I can't ignore it but how do I look passed it? I always feel like I'm on the bottom of the totem pole when I want to feel better about me and don't care what most negative oeoe have to say.....and advice?.....