We have to develop a strong mind and an ability to be able to see the pain in the body as one thing, and the mind and the awareness as something else. We have to learn to separate ourselves from the sensations in some way. It's also very helpful to have a strong practice in learning how to contemplate confidence inspiring objects when you have sickness or very strong pain in the body. Because if one has confidence, and reflects on these confidence inspiring objects and gets one's mind very concentrated on them, then you can have rests from feeling the sensation.
You'll have to take my word for it at this moment until you practice it. I've used this myself at times, especially when I've been very ill, to get a rest from the painful sensations in the body, to contemplate confidence inspiring objects, and I found that the mind can be having joy while the body is having lots of pain. It gives a bit of a rest to the mind so that it has the energy and courage to then be with the sensations for some time and to try to see into their particular characteristics. If we're with the pain all the time we may not be able to rest the mind, so that we can have the concentration, courage, and capacity to watch the moment to moment sensations.
Again, it seems to be the balancing of calm and insight factors in the mind, to know when you're getting exhausted watching strong pain in the body and to know how to rest the mind for a while. And to know how to separate the mind from the unpleasant sensations to get more calm, tranquility, and energy to be able to be with them until such time, I suppose that you die. But it means that you would have to train the mind in this capacity because if we wait until we're dying and we have strong pain and a painful death, we won't have the power in the mind to do this. So actually it's very helpful when doing the breathing meditation to practice on some of this unpleasant physical sensation and to also practice confidence inspiring objects of meditation that allow you to calm the mind at those times.