Perseverance is the real life expression of Self Discipline.
When we persevere in a task or exercise or diet then we feel better about ourselves.
Feeling better about ourselves equals increased confidence and satisfaction in oneself.
Increased self esteem then leads to a belief that we deserve more. If we believe we deserve more then we will discipline ourselves to persevere through another task or plan or diet.
Self Discipline leads to Perseverance that leads to increased Self Esteem that leads to increased self discipline.