We never keep to the present. We recall the past; we anticipate the future as if we found it too slow in coming and were trying to hurry it up, or we recall the past as if to stay its too rapid flight. We are so unwise that we wander about in times that do not belong to us, and do not think of the only one that does; so vain that we dream of times that are not and blindly flee the only one that is. The fact is that the present usually hurts. We thrust it out of sight because it distresses us, and if we find it enjoyable, we are sorry to see it slip away. We try to give it the support of the future, and think how we are going to arrange things over which we have no control for a time we can never be sure of reaching… . Thus we never actually live, but hope to live, and since we are always planning how to be happy, it is inevitable that we should never be so.
Pascal, quoted in this post offering a 17th-century perspective on the “quantified self.”