Living a life that matters doesn't happen by accident. It's not a matter of circumstance but of choice. Choose to live a life that matters.
A certain formula for an unhappy life is pursue someone else's definition of success. Until you define your own goals and purposes your life is not your own and there can be no sense of fulfillment no matter how much you achieve.
Don't sacrifice a good life for a good time.
Many things in life are not fair but all things should be.
I think Samuel Johnson had it right when he observed that hope is itself a species of happiness. So if we want to be happy it only makes sense to discipline ourselves to choose our attitudes, to think positively and to be hopeful.