Avos Perek 2

Rabbi Tarfon said: the day is short, and the work is plentiful, and the laborers are indolent, and the reward is great, and the master of the house is insistent.

(16) He [Rabbi Tarfon] used to say: It is not your duty to finish the work, but neither are you at liberty to neglect it; If you have studied much Torah, you shall be given much reward. Faithful is your employer to pay you the reward of your labor; And know that the grant of reward unto the righteous is in the age to come.

You can see that a man whose soul is afire in the service of his Creator certainly will not become lazy in doing the Mitzvot. Rather, his movements will be like the quick movements of fire. For he will not rest nor be still until he has finished completing the deed.

Reflect further that just like an inner fieriness of soul leads one to act with Zeal, so too the opposite, outwardly acting with Zeal leads to an inner fieriness of the soul. Namely, when one feels himself performing a Mitzva with great swiftness this will move his inner being to kindle aflame also, and the desire and want will increasingly intensify within him. But if he acts in a sluggish manner in the movement of his limbs, so too the movement of his spirit will die down and extinguish. This is something experience can testify to.

But for a man in whom this longing does not burn as it should, a good advice for him is to act with zeal by force of will in order that this will bring an inner awakening of this longing in his inner nature. For the external movement rouses the inner ones and certainly the external movement is more in his power than the inner ones. Thus, if he exercises what is in his power to do, this will lead him to also attain what is not in his power. For an inner joy will awaken within him and a desire and longing through the power of acting fiery, externally, by the force of will. This is what the prophet said- "let us know, let us run to know the L-rd" (Hoshea 6:3) and "After G-d they will go, who shall roar like a lion"(Hoshea 11:10).