I thought this out in my lucid last night. I was trying to jump onto a building but all my jumps failed. Then I had a moment of semi-brilliance. When I jumped, I looked up at the roof, but if it was a really high jump, I should be looking down at the roof. By keeping my head up, I already assumed my jump was too short. I looked down, assuming the roof would be below me, and it worked! I bet this concept would work on flying as well.