
“Be awful nice to 'em goin' up, because you're gonna meet 'em all comin' down.”
As quoted in The New Speaker's Treasury of Wit and Wisdom (1958) by Herbert Victor Prochnow, p. 409
Variants:
Be nice to people on your way up, because you're going to meet them all on your way down.
As quoted in A Quote for Every Day (2011) edited by Peter A. LaPorta, p. 41
Be nice to people goin' up, because you're going to meet them all comin' down.
Be nice to 'em goin' up, because you're going to meet them all comin' down.