How do you guys stop worrying?!

I know pregnancy is a wonderful time, but I'm a very anxious person and I can't help but think of all the things that can possibly go wrong. Each stage I pass I worry about the next. I worried about miscarriage, now that I'm further along, I worry about preterm labor, etc etc. It's so frustrating and I don't want to stress for my baby. Any advice on how to relax?