Dan really sucks. He never completed his training with Gouken. His father was a great fighter in his time but was killed by Sagat in a particularly gruesome match (Dan still cries about this regularly, think C-ko). Dan is consumed with thoughts of beating Sagat to avenge his fathers death. It is unknown whether his training stopped because he left to pursue Sagat, or if Gouken felt that Dan's intentions were unpure, and his spirit had been tainted by his overwhelming sense of hate for Sagat. Sagat himself serves as an example of what happens to good fighters when they choose that path.