"Dismal" existentialism?

Some think existentialism is bleak or despairing or (in Mitchell's word) "dismal," because it insists that we're each personally responsible for all our choices, and that those choices define human nature and possibility.The late Robert Solomon didn't see it that way. Check out his cameo in the film Waking Life, on this point. His book The Joy of Philosophy also addresses it:

But what is beautiful and revealing about... Camus (and Sartre, too) is precisely their refusal either to dismiss the question [of life's purposes and meanings] or to despair at the answer. They provoke an irresolvable tension, not between reason and passion but between our passionate commitments and our awareness that, nevertheless, our lives are ultimately not in our hands.