I find it VERY sipmle when I can relate to a character. Spunky fast characters like Reno from ff7 or Zell from ff8 I can write very well. If you know a character well enough they pratically write themselves, in a sense. But when it comes to a different personality, its not as hard as one would think. You don't have to relate to something in order to understand it, and as long as you understand it, it shouldn't be too hard of a time.