You need to be able to recognize when you are on the verge of cracking, and somehow ease off the pressure for a little bit.  Giving yourself a night off from your responsibilities, taking a slow walk with no heart rate goal in mind, indulging in a mid-week glass of wine.  All of the things that we may not allow ourselves to do because we have too many other responsibilities to handle; those are the things that become the most critical tasks when we approach the breaking point.