Love.

1) Love is an unconditional feeling. Its a special bond that has no limits, no rational. Its not just between a boy and a girl, its anyone special to you. I believe that love can change a person. It could change them for the better or for worse, but it is a timeless feeling that never really goes away.

2) Morrie mentions when Mitch and him are having a discussion about life's push and pull that love always wins. I think that he means that no matter the circumstance there is always something to take away from love. Even if its a bad experience, love is something to be cherished, it always wins.
Morrie later add that the most important thing in life is to learn how to give out love, and to let it come in. Morrie is learning to give and receive love in his limited time. "Love is the only rational action" Morrie quotes.

3) Love is a tricky thing. It can lead you blindly into hurt. But I believe that after you have time to recollect on your experience you'll find that any love is worth a place in your mind. A small place that will never be touched or changed. Its a comfort to those who believe they lost time by loving. So in a way, love does always win. It could cause hurt and sorrow, but it can cause joy and happiness if you let it.
The most important thing in life is to give love and be loved in return. There's no other feeling. It is a hard thing to give your heart to someone, there is always a hidden fear that that person will not take care of your heart. Love is a leap of faith. There will always be second guesses and doubts, but life goes by in seconds. Morrie is learning this through his condition.

4) Is it possible to fully give love to someone and be happy?
I have always wondered this question. I'm confused by the idea of spending your life with someone. That person would have to love all the little things, not just the obvious lovable things. Perhaps this is why we make such a big deal about dates and first impressions. Maybe we are afraid that no body could love the little things.