I think to go through "something", a single event, or events through out life serve to strengthen us and shape us in many ways. I think to suffer continuously serves to wear one down. Think of it like exercise. If you work out with weights and get some cardio in at a moderate level on a regular basis it improves you, if you exercise obsessively, say several hours each day and never take breaks even when you are injured you will break your body down thus suffering sometimes serious problems later.
Some people suffer and never get a break from it. Some go through something and make a recovery, and go through something else later, make a recovery repeat. If there is no recovery or relief people break down mentally and emotionally. They become exhausted and lose their will to continue. Just my theory.