WHY YSK- Many people practice mindfulness and meditation as part of their lives, and some would like to but feel like they don’t have time to sit down and meditate properly. Once you’ve gotten used to doing it as a part of your daily activities, it becomes easy to simply take a few breaths and gain some peace from your everyday existence. You don’t need to wait for a time when you can sit and clear your mind completely. It’s a nice bonus, but not necessary for living a mindful life.
I don’t know, it’s worked fine for me to do before bed as well. My body hasn’t conditioned itself to sleep when I meditate. I think it’s a good potential side effect to be aware of, but I wouldn’t recommend against it.