Yeah. It's called life. You do what you can, you do the best you can, and when you're knocked on your arse, you pull yourself back up and do it again. More often than not, the problem is extracting one's head from one's behind, and worrying about things you cannot change tends only to fuel this unfortunate predicament.
But more productive ways to deal with stress: For me, I decide whether I can actually do something about the thing I'm stressed about (e.g. what's the problem, can I solve it) and then I outline a plan to do just that (e.g. Problem: uncertainty about getting in to med school bc of grades; Solution/Ends: Get better grades, Plan/Means: outline course schedule, study plan broken down to daily activity lists blah blah blah; Methods for measuring Progress etc....).
If it's something I can't solve (or just anxiety in general), then I rely on a series of skills I've developed over the years to deal with mental stress. I have learned that the mind can be trained like a muscle. You must teach yourself, as one does a dog, to "drop it". You get better (as does the dog) with time.
And of course, the best remedy to a problem is prevention: lead a healthy lifestyle, good food, regular exercise, strengthen your bond with your religion/friends/whatever, practice meditation, etc...
Also, realize the great world doesn't care about you, you are not a unique snowflake. Which means you (mostly) make your own world. That is, though some things are left to chance, for the most part, you make your own luck, and that's something over which you actually have (a fair amount of) control. Rejoice in this, and start working, friend.
Lastly, life moves on, whether you're ready or not. And while this seems scary at times, I also find it quite comforting, knowing that even the worst shall pass.