Recognize that you lose efficiency when you try to work too many hours. Take a break, take a nap, then go after it again. Learn to delegate well. This doesn't mean simply passing off work you don't want to do. It also doesn't mean continuing to be involved in every step of the work delegated. Pass work to others who are well equipped to do it, have them report progress (or lack thereof) on a regular basis, and go on with work only you can do. Even if you can do certain things better than anyone else, be sure that the increased quality is worth the time invested.
Sometimes the easiest way to do good work is to do less work, when possible. Find a co-worker who you can trust. This is a matter of trust, and it is vital for your well-being in a demanding environment. Make sure your trust is not just established among your coworkers, but with others in your industry and in your workplace. The more people we are comfortable with the less stress there is to maintain high productivity levels. People who you are comfortable with who are not in your profession, but who still feel comfortable with you, are likely to do good work with you in a demanding environment. If you do feel uncomfortable about a co-worker, it is time to find another one. This leads to another problem: Many people, especially those in the workforce, are under the belief all they have to.