Nothing zonks me out like an intense play session. After a scene of spanking, knife play, and bondage (among other things, but those are a few of my favorites), I always sleep like a baby.
Conversely, nothing perks me up in the morning like an energetic bout of (mostly) vanilla sex. After that, I'm ready to go face the day!
The lesson is: sex and/or BDSM is appropriate for any time of day, and you should do it as often as possible, ideally multiple times a day.