"The unhappy person is one who has his ideal, the content of his life, the fullness of his consciousness, the essence of his being, in some manner outside of himself. The unhappy man is always absent from himself, never present to himself. But one can be absent, obviously, either in the past or in the future. This adequately circumscribes the entire territory of the unhappy consciousness."
"The unhappy one is absent. But one is absent when living in the past or living in the future. The form of expression is important, for it is evident, as philology also teaches us, that there is a tense that expresses present in the past, and a tense that expresses presence in the future; but the same science also teaches us that there is a pluperfect tense in which there is no present, as well as a future perfect tense with the same characteristics. These are the hoping and remembering individuals. Inasmuch as they are only hoping or only remembering, these are indeed in a sense unhappy individuals, if otherwise it is only the person who is present to himself that is happy. However, one cannot strictly call an individual unhappy who is present in hope or in memory. For what one must note here is that he is still present to himself in one of these. From which we also see that a single blow, be it ever so heavy, cannot make a person the unhappiest. For one blow can either deprive him of hope, still leaving him present in memory, or of memory, leaving him present in hope."
- Kierkegaard (Found on Brain Pickings: https://www.brainpickings.org/2014/05/05/kierkegaard-on-presence-unhappiness/?mc_cid=ba67bb2263&mc_eid=1a9434ef39)