We shouldn't discount the mental aspect of it. Even some big guys just can't punch with real power because they don't have the mentality for it. Some time with a punching bag and some partner work with mitts will take of that.
Even though I think I've always had a pretty good mental approach to it, that kinda training lifted my punching power greatly. That refining initially happened when I was training Wing Tsun and spent a lot of time working on just that kinda stuff. Of course, now I train Bajiquan and Chen style Taijiquan and the jings are so very different.
Anyway, I think the most basic root for intent, as in the Internal arts, lies in this mentality.
"Once you get deeper into the study of Kung Fu you will realise that lineage and insulting others become more important than actual skill and fighting ability." -- Tai'ji Monkey
"Eh, IMO if you're bittching about what other people are doing instead of having intelligent (or stupid) conversation about kung fu or what your favorite beer is, you're spending too much time exploring your feminine side." -- Meat Shake