There has to be some other teacher out there. Maybe they won't accept outright, but if this guy has turned you down so many times, I'm sure there are other ways to learn.

Relying on only one person is bad news, anyways.

[Or at least, that's how things have gone for him. Having a mentor who didn't want to teach him, and didn't really put much thought into how Gokudera learned had result in some pretty dangerous losses. There are things he's taught himself and he's succeeded, but still... there are a lot of lessons that were tough to swallow, no matter who handed them out.]