Horace, Epistles 1.2.40-43
dimidium facti qui coepit habet; sapere aude,
incipe. vivendi qui recte prorogat horam,
rusticus expectat dum defluat amnis; at ille
labitur et labetur in omne volubilis aevum.
He who makes a start has the job half done; dare to be wise! Begin! He who postpones the hour for living aright is a bumpkin waiting for the river to stop; but it flows and shall flow, rolling along for all ages.