The following quote from C.S. Lewis is one of the sections of his book, Mere Christianity, that most changed my worldview back when I was 16/17 years old.
If you think of this world as a place intended simply for our happiness, you find it quite intolerable: think of it as a place for correction and it’s not so bad. Imagine a set of people all living in the same building. Half of them think it is a hotel, the other half think it is a prison. Those who think it a hotel might regard it as quite intolerable, and those who thought it was a prison might decide that it was really surprisingly comfortable. So that what seems the ugly doctrine is one that comforts and strengthens you in the end. The people who try to hold an optimistic view of this world would become pessimists: the people who hold a pretty stern view of it become optimistic.
This whole idea brings up a lot of other questions though, and some objections… which I don’t even have time to list out. So I will just leave this quote here, and say I like it.