BEN AZAI said: One who bears in mind the following four things, and never loses sight of them, will never sin namely, whence he came, and whither he goes, who is his judge, and what will become of him. Whence he came?,--from a place of darkness; and whither he goes?--to darkness. Whence he came?--from a dirty place; whither he goes?--to make unclean every one who will touch him. Whence he came?--from a fetid secretion, and from a place which is invisible to a human being; whither he goes?---to sheol and Gehenna, to be, burned in fire. And who is his Judge? Remember that his Judge is not of flesh and blood, but the Lord of all the creation, blessed be He, before whom there is no, iniquity, no oblivion, no consideration of person, no, bribery. And what will become of him?--worms and maggot, as it is written [Job, xxv. 6]: "How much less the mortal, the mere worm? and the son of earth, the mere maggot?" R. Simeon said: A human being has worms in his body when alive--i.e., lice, and he is converted into a maggot after his death.
R. Eliezer b. Jacob said: Think of a big palace in the centre of which the vat of a tanner is placed: so is a handsome and respected man who lets an unbecoming word pass his lips. If a human being would issue from his body perfume (instead of excrement), how would he pride himself against all other creatures? (So, if this man allows his lips to pass only respectable words, he can pride himself.) When R. Eliezer was about to depart, his disciples paid him a visit and requested him to teach them only one more thing. And he said unto them: Go, and be careful, each of you, in honoring your neighbor; and when you are praying, remember before whom you stand and pray, and for the observation of these you will have a share in the world to come.
Sources: Sacred Texts