Perspective of life

How one lead their life really depends on their perspective of life.
A happy life? A remorseful life? A fulfilling life? A "bitter" life?
I think first one must learn how to look at the cup of milk as half filled instead of half emptied.
Then one can look forward to filling up the cup with milk and not sulk over the other emptied half.
That is one thing I have to learn. Tough for a pessimistic person like me. Must be in the genes.