Every preparation that a person does in a anticipation of a mitzvah is in itself a mitzvah. Therefore anyone who does everything for the sake of Heaven is constantly engaged in a mitzvah. How proper it is to verbally proclaim before every deed that he is doing it as a preparation for a mitzvah. For example, before eating, one should say, “I hereby am about to eat and drink so that my body will be healthy and strong for the service of Hashem, may He be blessed.” Or, prior to sleep, one should say, “I am hereby lying down to sleep so that my mind will be clear and settled to serve Hashem, may He be blessed.” Before engaging in business, one should say: “I am hereby going to do business and to endeavor to earn a livelihood with the help of Heaven, so that I can provide for my family as my Master commanded me, and to enable me to do tzedakah and acts of kindness as well as all the mitzvos as they are meant to be kept.”
The same can be done when a person builds a house or makes a new garment or the like — really any action that a person does. The person’s words will bear fruit, for by making this verbal declaration spirituality and holiness will descend upon all his physical things and it is counted as a mitzvah. Not only that, but the person will even get reward for all of these words of his. All this is true provided that one’s deeds match his words — that he does not eat and drink excessively but only as a tzaddik who eats only to sustain himself; that he does not sleep too much; and that he is not bent on becoming overly wealthy, for then one’s deeds show that his words were not honest, and the One Who sits in Heaven will laugh about them.
Also, since the person is acting for the sake of Heaven, he must take care that what he does be a mitzvah not a sin. He should be careful that his eating and drinking and his business affairs all be in accord with the law and Halacha — then it will be counted as a mitzvah and he will receive reward for his actions. He should also take care to choose those foods that are beneficial, not what may taste good but is actually detrimental to his health. For besides the fact [that eating unhealthy food] is not the [will of Heaven] and it cannot be considered a mitzvah, the person will also be punished for transgressing the Torah’s admonishment of And you shall be very careful with yourselves.