From my perspective, "happy life or a relevant, contributing life" is a false dichotomy. For one reason, self-care is of vital importance to truly be contributing. Burning oneself out on "contributing" does no one any good.
And "relevant" to whom? "Contributing" to what?
An important perspective on this, from my view, is Principle Doctrine 5:
It is not possible to live a pleasurable life without the traits of wisdom, morality, and justice; and it is impossible to live with wisdom, morality, and justice without living pleasurably. When one of these is lacking, it is impossible to live a pleasurable life.