Choose the course which you adopt with deliberation; but when you have adopted it, then persevere in it with firmness.

Bias of Priene (fl. c. 650) Greek philosopher

In Diogenes Laërtius, The Lives and Opinions of Eminent Philosophers, “Bias” (c. 230) [tr. Yonge]

Alt. trans.: "Be slow in considering, but resolute in action."