The way to attain this trait, of having enthusiasm and love for all that is holy, is by consistently reading works of mussar-ethics and by regularly engaging in Torah and good deeds. Eventually, once the person accustomed himself to even one practice of piety or holiness and then one day he was unable to do it, it will seem to him as if he was not a Jew on that day. But when the person becomes lax, then his enthusiasm and love will wane day by day until, eventually, it will be very difficult for him to guard and keep [mitzvos]. Moreover, he will feel as though it is perfectly permissible to refrain from doing a mitzvah and from learning Torah or to commit any sin. One must therefore be strong and courageous to vigilantly keep the Torah and Divine Service. And if one’s Evil Inclination attacked and overcame him, let the person strengthen himself again and grasp the path of the righteous — the path of the holy. When someone is about to fulfill a mitzvah that came his way, he should prepare himself first by thinking thoughts that arouse the heart to do the mitzvah with enthusiasm, love and great joy. Better yet, let him say out loud: “This is my duty and it is appropriate for me.” He should also do external movements with his body and motions with his hands, for external arousal generates internal arousal. It is well known that one who comes to purify himself receives assistance from Above and that one who sanctifies himself below is sanctified from Above; one mitzvah leads to another mitzvah, and “everything depends on the abundance of good deeds” (Avos 3:15).
However, when it comes to the affairs of this world, one should not have enthusiasm and love — for it is all vanity and vexation. Instead, one should do whatever he has to do as the he was forced by a sheid, without enthusiasm or love.