Running a business is very stressful, the lesson I have learned is to pace yourself and make taking breaks mandatory. If we work like machines, we'll feel like a machine... It's very unhealthy.
The downside to that can be pretty large though. Burnout is always something that can happen when you work too much. Once you get to the point where you feel burnt out, you let things go and stop giving a ****. So the key it seems is to find that happy median between working and getting things done and taking a rest as well to not be all consumed by work.