To me, remembering bad things that have happened to us give us a gist of hope and despair.
Sometimes hope, because it gives us the idea to cling on, to believe that there are bad times but without them we wouldn't have the better things in life. It gives us hope that something else happens, something positive. A chance that we may be able to have a cherishable memory to remember by.
But it also leads to despair. Sometimes we don't think positively and we only believe that life only gets worse. That there are no more chances of good things actually happening anymore.
Remembering is powerful. Remembering bad things, well that leads to two paths in which our minds lead us in on their own.