It happens to just about everyone. You either see it coming, or it catches you completely off-guard.
Someone you know asks you out, but you could not be any less interested. In fact, you are looking for a relationship.
I get why you did it.
But using that line is pretty terrible. Maybe even the worst thing you could have done except maybe laughing.
That maybe, in the far off future, you will be ready for a relationship. And wait he will. What a waste of time, right?