As you put points into Body and Mind it effects your overall skill points and checks. It also has an effect on the cost of leveling up your skill points. You can increase the individual skills first and then increase Body or Mind as needed but in the long run it can take more XP. Many of us have found it works better to max out Body and Mind then work on the other skill sets they control. Your character class will also favor one of these so it's best to focus on that one first. In the simplist terms the higher you can get the number, the better.