Have you ever met someone who despite a hard life and circumstances they find themselves in, they have a true happiness. Not some fake mask they put on when they are in public. Whether its loss of health, financial problems, relationship problems, death of a family member... whatever may be happening in their life that person seems to be at peace and seems genuinely joyful.
In the bible one person comes to mind that we could learn from. Paul. Paul always seems to be in a difficult situation, spending much of his ministry time in prison. However, we read his letters and we feel the peace that he had even in the worst of circumstances.
I challenge you to read the book of Philippians and other letters he wrote and reflect on how you would feel in those situations. Paul always kept his eyes on the eternal. He was willing to sacrifice his life on earth with joy, knowing there will be better things to come.
This is something non Christians don't have. There is never any assurance of what will come when they die. Whether they believe in another Religion or don't know what to believe they will always have to wonder if they lived a good enough life as their religion requires. This is something that Christians should not worry about. If you declare Jesus as your savior keep things in the right perspective. Always knowing that no matter what happens here in this life your eternal life is set for the better.
Here is a video that i saw a couple years ago and recently used at the Zone Rally. The preacher's name is Francis Chan, and he has a way of putting things in the right perspective.