I agree with Thal, too. If your stress levels are so bad as to be impinging on your life and making you miserable, you need to find someone to help you. Maybe your doctor'd be a good start.
So far as the stuff you can't control goes... accepting you can't do anything about it probably won't necessarily stop you worrying about it but it will make it easier to handle. The stuff that you can control... make a decision and whatever you decide, get on with it and weather the storm if you have to.
I work with a lot of performers, and I think one thing they'd all agree with is that making a living in performance is hard. Many find the trick is to diversify. Most of the performing musicians I know also teach, play background music in bars or at weddings, play for dance classes, play for other theatre companies in rehearal or performance, accompany for other musicians... A ballet dancer of my acquaintance also runs a sucessful business on the side designing clothes for dancers. A lot of ex-dancers end up retraining as masseurs or physiotherapists, or teaching dancing or tai chi or pilates. The point is, don't just see performing as playing concertos with good orchestras, or recording a CD or two. Find more ways you can approach your music than that, and accept that it's not going to be the easy choice but if you put the work in and make it work, you'll have a fulfilling life and something you can really be proud of.