Pain is not negated by the presence of a greater pain somewhere else in the universe

I am assuming this node was created to discuss emotional pain, not the physical variety. Diminishing the validity of another person's pain is not something that any person has the right to do. Yes, there is probably most definitely someone else in the world who is suffering much more intensely than you are at this moment, perhaps more than you will ever suffer in your life (if you're lucky), but at that moment you are concerned with your own pain. Selfish, perhaps, but also human.

You are the center of your own universe.

Yes, at one point in your life you feel as if your world is crashing down around you and in hindsight you think, that wasn't so bad. At the moment the pain occurred, it shattered you, and someone else being in worse shape than you are doesn't take away from the fact that you were shattered.

And I'm willing to bet that you both survived.

More importantly, other sort of pain comes from failure. Failure is lack of success, and success can only be evaluated with comparison to other people. And in like any competition, you can win in two ways: improve your score, or lower competition's. And since your pain came from failure, if there's someone else who's in as much pain as you (or preferably more), it must mean he's as much of a failure (or more so). That, in turn, increases your relative success score slightly. You've won.