don't let the grass grow under (one's) feet
Be continually active; do not stand still or be idle (thus giving the grass a chance to grow where you're standing). Don't let the grass grow under your feet, kid. Get to work!
don't let the grass grow under your feet
Act with dispatch; don’t delay. This expression dates from the sixteenth century. It appeared in print in 1607 in Edward Topsell’s natural history, Foure-Footed Beasts (“The hare . . . leaps away again, and letteth no grass grow under his feet”).