"Just think about baseball" is actually a common-enough reply when someone's trying to mentally think unsexy thoughts. "So I think about baseball" and variations are when someone's saying what they did/do in a situation.
Frank Drebin and Jane from the first "Naked Gun movie."
Jane: I've heard police work is dangerous.
Frank: It is. That's why I carry a big gun.
Jane: Aren't you afraid it might go off accidentally?
Frank: I used to have that problem.
Jane: What did you do about it?
Frank: I just think about baseball.