That's the key to life. We have to let it all go sooner or later. Some things may seem like the biggest thing in the world one day, and completely insignificant the next. And if you think of it on a long enough scale, everything is insignificant at some point. So let it go. Let it all go. Don't dwell on it and move on to the next thing. Sooner or later you'll have to let that go too, so be sure to enjoy it while it lasts.