I think sometimes that it's easier to live in sweeping theories and in impossible expectations than it is to live moderately in an immoderate world. If one sets one's goals unrealistically enough, then one can assert that (a) all worthy goals are unattainable and (b) all goals which are attainable are unworthy. The resulting frustration gets kinda comfortable, like a huge scab over a wound that festered way too long.
Living in moderation, though, struggling to find one's values and one's life both are workable--much more challenging, and yet much more worthy. The middle way--to live in this world, awful as it is, and try to steer things towards the good--is the Way. It's unromantic, this middle way--it's just what works.
But it lacks the radical highs and lows which appeal so much to the doomsayer or the triumphalist. It requires perspective. As Horace says "be resolute when things are going against you, but shorten sail when the fair wind blows too strong".
Seventy to ninety years, this all lasts, if one is particularly fortunate. That's not long enough to live in frustration and still live at all. It's far too long to live in disappointment.