This representative quote has been reprinted many times elsewhere, with good reason, so I have no qualms utilizing it here:
Hope in this deep and powerful sense is not the same as joy when things are going well, or willingness to invest in enterprises that are obviously headed for early success, but rather an ability to work for something to succeed. Hope is definitely not the same thing as optimism. It’s not the conviction that something will turn out well, but the certainty that something makes sense, regardless of how it turns out. It is this hope, above all, that gives us strength to live and to continually try new things, even in conditions that seem as hopeless as ours do, here and now. In the face of this absurdity, life is too precious a thing to permit its devaluation by living pointlessly, emptily, without meaning, without love, and, finally, without hope.