Motivation For Study
Personally, I think two methods help me most.
1) Take a break. I don't mean go on Facebook (or Quora, for that matter). Really take a break. Go watch a mindless TV show for half an hour (but no more than that!); take a shower; go outside and walk around your block; lie down for a few minutes. Take all the don'ts that you've forced yourself to go through in order to study, and pick the one you most want to do. Then do it. And then get back to studying.
2) Fall in love with what you're studying. This is the most effective tactic I've ever found. When I'm genuinely interested in what I'm reading/learning, time flies and so do the pages. When I could not care less, time doesn't seem to be passing at all and nothing enters my brain. If you're in college or beyond and find yourself in a situation where you honestly cannot come up with one reason why you should be fascinated by what you're doing: think long and hard about whether you should keep doing/studying it.