The way I see it is you have two choices in life; you can be grateful for everything life has given you or you can be resentful for everything life has done to you. Your degree of happiness is directly proportional to the conviction of your choice
Achievement of your happiness is the only moral purpose of your life, and that happiness, not pain or mindless self-indulgence, is the proof of your moral integrity, since it is the proof and the result of your loyalty to the achievement of your values.
Nobody grows old merely by living a number of years. We grow old by deserting our ideals. Years may wrinkle the skin, but to give up enthusiasm wrinkles the soul.