This has been my theory from day 1, he's like Superman from Man of Steel. He's quoted as saying "I'm as strong as I need to be" + the way his powers evolve / appear is basically him adapting to whatever he needs at any given moment. The difference is Superman's upper limit is WAY higher (if it even exists), and because of the nature of his solar energy absorbing "ability" he never "loses" what he's already gained. MC on the other hand has so far only "consciously" retained his night vision and his moderately increased strength (and penis
) because he's continuously using them. As Harper said, practice makes perfect and all. I suspect if he were to somehow manage to activate that force field on purpose and "feel" how he did it, he could practice and be able to get it to manifest at will.
...or maybe I'm totally wrong and his superpower is actually cooking ramen or something.