Often we call our life of an "imprisoned self" discipline. However, discipline is a result of, not a cause of, death to self, not imprisonment. We are no longer enslaved slaves. It is not a dead self we have to fear but an imprisoned self which is infinitely more self-cantered than any other(Proverbs 19:2).
Imprisoned intensifies the focus on ourselves and demands even more from whom and what's around us.
A disciple or learner is taught death to self by knowledge of Him(Galatians 2:20, Isaiah 53:11) and the resulting discipline is an abundant life under the power of the Holy Spirit.