2) How much management responsibilities do you have along with your development responsibilities? How much of these can you delegate. Perhaps you've got too much on your plate and your attention is divided too much to really think/focus on your duties. Perhaps you can't complete anything because you have too much and that's what's stressing you out. You could code another 100 lines today, but you know or feel that that's still not enough to complete the task. Find a way to divest yourself of some responsibilities/obligations in a way that still lets the work be done (rather than being undone and in your queue).
3) Counseling. It's not a four-letter word. Someone to talk to, voice your concerns to, and trust. If you're religious, your priest or minister. If you're still close to some friends outside your company, perhaps from college or something, that can be your confidante, then that's a good option too. But I still prefer the counselor approach. They're trained to help you.
4) Like tmaly said, something outside work that's not programming/computering/managing. Being able to shut your mind off for an hour or two while going for a hike or a jog or cleaning out weeds in the garden is remarkably restorative. It pairs well with things like meditation. In fact, once the act becomes rote then it becomes meditative. The mind is free to wander while a minimal portion of the brain focuses the body on the act.