Unless you try to do something beyond what you have already mastered, you will never grow.
— Ralph Waldo Emerson

Undertake something that is difficult; it will do you good. Unless you try to do something beyond what you have already mastered, you will never grow.
Ronald E. Osborn mastered quote

Technique is noticed most markedly in the case of those who have not mastered it.
— Leon Trotsky

He who controls others may be powerful, but he who has mastered himself is mightier still.
— Lao Tzu

Difficulties mastered are opportunities won.
— mastered quotation by Winston Churchill