Work on Oneself

You must educate your body with your head, consciously. It is very simple. Never allow it to do what it wants. You make it do everything contrary to that which it loves. It likes sugar, you do not give it any. One must inure it to struggle, you are always right when you resist your body. It is simple. Everything contrary;
Under all conditions, in all political situations, man must educate his body to be submissive to him. Your personality can educate your body. He in which the body is strong and has the initiative over him, this one is null. He who has his body enslaved is intelligent. You understand what is meant by intelligent? Intelligent means he who directs his body. If the body directs, you are a nullity, a peasant—if you direct your body you are intelligent. Thus, choose what you want. Intelligent or peasant? If you want to be a peasant, let your body direct you. If you want to be intelligent, let your consciousness direct your body. The more you want to direct your body, the more it opposes you. And in resisting you, the more strength it gives you.
Paris Meeting 22. July 1943

You must suffer physically. For instance, don't eat enough; be hungry. Or, if your organism doesn't like cold water, make yourself bear cold water. Same with hot water. Do the opposite of what your body is in the habit of doing. Make it suffer. It is the one and only way to make the force you lack. Not a mental suffering. We have seven kinds of suffering. For you, bodily suffering is necessary.
Paris Meeting 20. April 1944

One needs fire. Without fire, there will never be anything. This fire is suffering, voluntary suffering, without which it is impossible to create anything. One must prepare, must know what will make one suffer and when it is there, make use of it. Only you can prepare, only you know what makes you suffer, makes the fire which cooks, cements, crystallizes, does. Suffer by your defects, in your pride, in your egoism.
Paris Meeting 7. December 1941