For me, it's because it's the start of another whole day of .. not wanting to be here, and as the day goes on, I do tend to feel better too, I feel better knowing it'll get dark and I can sleep/escape but also I am calmer in the night when everyone else is asleep and there are no pressures from other people. Daytime is too busy, too much going on, too much that can go 'wrong' I guess.