And a final meaning of self-discipline is to choose our attention and focus. To this reasoning and feeling follows. Attention and awareness is closer to the deeper true self.
This, of course to work and result in to action, presupposes that we do not betray true (not interpolated) consciousness. And consciousness is betrayed when we do not take decisions and commit actions that correspond to it.
Furthermore, the persistence and perseverance is a proved form of self-discipline!
So here it is! Do you have perseverance in an effort? There is to be found also strong self-discipline.