The people who say "Every cloud has a silver lining" aren't always hopeless optimists who don't know what else to say. Quite often, they're right. Maybe that "silver lining" isn't something that makes up for a tragedy, and maybe it's not something that makes you feel justified in the struggles you've experienced. However, fortunately, and frequently, that silver lining is perspective.
Some people learn perspective when they're four and others when they're 64. Once they acquire perspective, whether through tragedy, regret, or something else awful, they realize how important it is, and wonder how they lived without it.
Perspective reminds us what's important and what's not. It helps us recognize that we probably don't need to dwell on one bad grade for too long, or wallow for months on end about a relationship that we knew wouldn't work out in the first place fulfilled its prophecy. It allows us to move on, to not sweat the small stuff, because the bigger, life-altering problems are still looming.
The thing about perspective is that it doesn't make the problem that caused it go away. It doesn't fix the tragedy, or the struggle, or the regret. What it does is it allows you to live the rest of your life, from the moment you truly gain perspective forward, with more level of a head. It reminds you of what's actually important, like the fact that you should take the time to be kind to people because you never know what they're going through, or how much time they have left. It reminds you that you shouldn't spend hours in agonizing worry over something that should have been decided in three minutes.
Basically, what perspective does is organize issues for you. It allows you to clearly (or, at least, more clearly) see which problems are big and which are not. It can be frustrating when other people can't see clearly, but perspective allows you to help them. In the heat of what can seem like the largest tragedy or the largest curse, perspective can save you, or can at least be something you gain when it seems as though all else is lost.