This statement in itself seems contradictory from first glance. But when you really dig deep into its meaning you get the idea. There has been plenty occasions of great suffering during America's history alone that has each its own great reward. Take the Revolutionary War for example. Many suffered and died but from that war America gained its independence from England. During the Civil War, out all its despair, accomplished the eradication of slavery. We can not forget WWII. A lot of death, suffering, and sorrow came from that war but Jewish and the tortured people by Adolf Hitler finally came to an end. So it can be said that from great suffering comes great rewards. It just depends on your perspective.
This doesn't only apply to wars and and worldly matters. It can always be seen through the lives of each single person on a daily basis. Each person has their own cross to bear and the suffering that goes along with it. During our times of sufferings we can not see what reward can possibly come from it. I doubt the men fighting in those wars didn't visualize, on an individual basis, what reward would come out of their suffering. It is a hard thing to realize when you are actually going through the suffering. But in hind sight it is always clear. Sometimes, if you are able to take a step back from your own personal struggle you might catch a glimpse of the good that can come out of it. During times of struggle, when things seem so unbearable, we must train ourselves to take that step back and see the bigger picture. It's puts it into perspective and the cross we carry does not seem quite as heavy anymore.
Another way of trying to remind yourself that good can come out of a horrible situation is by reading inspirational stories of people from all walks of life and how they got through their own personal challenges. It gives you hope and we all need hope. It is our life line. Keep clinging to it and you will find your way through the dark.