You can say "Carpe diem", the famous quote from latin poet Horace. It literally means "Seize the Day" but in the context it was used means "Seize the Moment".
Seize the moment was a very common idea for Roman authors, but the classic example is found in Horace's Odes Book 1 ode 11. That phrase is rendered carpe diem, which literally means seize the day.
