Why do some people find playing a song very easy and others find it exceedingly difficult? I think it's because as we practice we are basically trying to crack the code of a piece. Some will understand it immediately, for some it takes a moment, and some never seem to get it. The best part of all, is once you have cracked one type, the next song in that style or genre is that much easier as you have the code partially cracked already. For that reason it's important to try many different styles of music.