I imagine one of the reasons people cling to their hates so stubbornly is because they sense, once hate is gone, they will be forced to deal with pain.
The value of physical pain is that it is finite. It ends when the ailment ends. We can use this as an opportunity to push on through, with the safety net of knowing it will eventually be over. It is practice.
Ryan Holiday. Just this weekend I was talking about the value of exercise qua mild self-harm. This is more articulate than I was.