This YouTube video (by Jayson Lowe) argues that everyone already demonstrates full discipline via their existing habits; those habits either support or harm their future, and harmful habits cannot be removed instantly but must be changed gradually. The clip emphasizes personal responsibility and the need for incremental habit change.
You are already 100% disciplined in your own set of habits. So you've already demonstrated that you can be 100% disciplined at something because you are 100% disciplined in your own set of habits. And those habits are either contributing to your bigger future or contaminating your bigger future. And you can't eliminate all the contaminating ones in one fell swoop. Won't happen.
