Board Thread:General Discussion/@comment-6252544-20160213233306/@comment-1916997-20160214042530

Magic is mostly a device for plot, as it is in all stories that have magic users. Let's not pretend this is a problem only Once has. As far as canon explanations, you could argue that magic is a mix of talent, emotion, mental focus, etc. so that explains how sometimes people do things, and sometimes they do other things.