Fitness has nothing to do with the way you look. Everybody has a different body type and a different way to gain muscle. I am a shorter stout man and I gain muscle very easily but its hard for me to get a six pack. Fitness is all about how you feel. Do you feel great and happy? If so, then you are fit. If you get angry when you are sparring then you are looking at sparring in the wrong way. Sparring is not a fight, it is a learning experience. You must treat each match as a way to polish your technique and work on control. You must treat karate as a battle with ones self not with an opponent. Don't look to be better than one person or be bigger than some one else. Train, learn, gain confidence, and make yourself better. Discipline is your beginning objective in karate, after you gain this, then you can truly start your adventure.