eric, I believe that when we come into this life, we came with certain soul promises. You have heard the saying, no pain no gain? Ok, think of it this way, as you progress through school, each class is a bit harder than the previous one until you attain the top. Ok, we must go through "hell" to gain enlightenment, and all sorts of slings and arrows of outrageous fortune will be visited on us on the way. Each incarnation is tougher than the previous one.

Or, if you prefer, "I saw starving children and I screamed at God. Then I realized that those starving children were God screaming at me"!

Finally, if you prefer, nature is not cruel; nature doesn't care.