Mitzvos, Our Link to Hashem
The main significance of the mitzvos lies in the fact that Hashem Himself gave them. They are therefore the only means through which we can approach the Creator, and we draw spiritual nourishment from performing them. If we keep the mitzvos with the intention of drawing close to Hashem, they have life and a soul. Otherwise they are empty rituals, bodies without spirit.
Source: Meor Einayim, Parshas Vayeira