For me, it's luck if I wake up on time. I set 3 alarms on my phone and put it across the room so that I'll have to get up and walk over and back in order to turn it off. If my subconscious isn't being a troll I'll wake up, but more than likely my subconscious will take over and I'll wake up 3 hours later with every alarm turned off, and no memory of such events at all.