Sounds like meditation techniques. I often practice mindfulness meditation in a dark room for ~10 minutes in the mid-afternoon when I get tired. It usually gives me new energy and focus similar to if I'd napped.
After having one course of zen meditation, it seems to me meditation is pretty much the complete opposite of falling asleep. You want to stop thinking about anything, but only to feel perfectly aware of the current time and place. And your mind becomes completely focused and concentrated on.. nothing. In particular, the part in the OP where you "picture yourself being on lake, etc" looks to me as completely anti-medi…
see http://marc.ucla.edu/mindful-meditations "Body Scan for Sleep" for example