Light is important. As little as 0.5 lux shining under your Door could be enough to suppress your pituitary from releasing hormones, if it is otherwise dark in your room and the duration is longer than an hour. You actually have a whole other set of receptors that aren't involved in vision but instead signal your pituitary. Also, getting light during the day is part of this signaling as well. The strongest reaction is from 470nm light, but there is some effect from ~500nm to ~450nm. (To me, 470nm light looks like the really deep blue sky on a perfectly cloudless day.)

Don't just depend on f.lux! You're probably still shining the wrong kind of light directly into your eyes. I put on blue blocking glasses an hour after sundown, but it's just best to limit your screen use at night. (There's a pair of $8 Uvex safety goggles that do a good job with blue light. They still let in a little green, however.)