An excerpt from C.S. Lewis Screwtape Letters.
The humans live in time but our Enemy (i.e., God) destines them to eternity. He therefore, I believe, wants them to attend chiefly to two things, to eternity itself, and to that point of time which they call the Present. For the Present is the point at which time touches eternity. Of the present moment, and of it only, humans have an experience analogous to the experience which our Enemy has of reality as a whole; in it alone freedom and actuality are offered them. He would therefore have them continually concerned either with eternity (which means being concerned with Him) or with the Present—either meditating on their eternal union with, or separation from, Himself, or else obeying the present voice of conscience, bearing the present cross, receiving the present grace, giving thanks for the present pleasure.
(2) Our business is to get them away from the eternal, and from the Present. With this in view, we sometimes tempt a human (say a widow or a scholar) to live in the Past. But this is of limited value, for they have some real knowledge of the past and it has a determinate nature and, to that extent, resembles eternity. It is far better to make them live in the Future. Biological necessity makes all their passions point in that direction already, so that thought about the Future inflames hope and fear. Also, it is unknown to them, so that in making them think about it we make them think of unrealities. In a word, the Future is, of all things, the thing least like eternity. It is the most completely temporal part of time—for the Past is frozen and no longer flows, and the Present is all lit up with eternal rays. Hence the encouragement we have given to all those schemes of thought such as Creative Evolution, Scientific Humanism, or Communism, which fix men’s affections on the Future, on the very core of temporality. Hence nearly all vices are rooted in the future. Gratitude looks to the past and love to the present; fear, avarice, lust, and ambition look ahead.