Self-discipline leads to higher spiritual states
Only if practiced with understanding.
The clearer the goal,
The greater the result.
We must distinguish between discipline with a purpose and blind discipline. Discipline with a purpose is merely a means to an end and is healthy. Blind discipline does not have a true purpose and so becomes fanaticism. In the past, there were many spiritual people who believed in harsh asceticism. They would flog themselves, live in cold and damp caves, twist themselves into uncomfortable postures, fast for dangerous periods of time. All too often, these people lost sight of their goals. We must be strongly disciplined, but we must not lose sight of our inner meaning.
Austere living with a clear understanding of why and how we are doing things does not require esoteric practices. Few of us mind going through extra effort and even hardship if we know that we will gain something better for it. That is all that discipline and austerity are about : You make extra efforts to gain a better life.