I meant in last night's episode. No reference to his other living student at all.Yamcha wasn't his student at the time.
I like to think that a combination of Goku heavily surpassing him and defeating him easily in the 22nd tournament combined with dying to Tambourine in one hit without being able to a punch broke his confidence. Doesn't help how everyone got ahead of him in Z.
Hard to be smug when you're in the lower echelons of power.
Krillin cleaned up his act way before that. He was crying when he though Roshi killed him in the 21st tournament.