Based on Bhagavad Gita Chapter 02, Text 59
Attaining self-mastery — bending our impulses to our principles — is vital for us to make tangible spiritual progress. On the devotional path, the means that we choose to strive for self-mastery are especially important.
There are two broad ways to self-mastery:
As determination’s feat: We see self-mastery as a peak for our willpower to scale. As our focus is only on our own will, the only higher pleasure that we can get in our bid for self-mastery is the pleasure of the ego, the self-centered exultation of having conquered our desires. Self-mastery, if achieved, often increases our ego, and makes us look down contemptuously or at least condescendingly at all those who cannot perform feats of determination like us. The self-centeredness, the infatuation of the ego and the condescension towards others — all these make our heart inhospitable for Krishna, and so deprive us of any substantial devotional progress.