Take time by the forelock

Seize the present moment. Old Father Time is represented as being completely bald except for a lock of hair on his forehead. You cannot catch him from behind but you can catch him from the front by seizing him by the forelock. This proverb means that time past cannot be used, but advantage can be taken of it now.

See also:

• There is no time like the present
• A mill cannot grind with the water that is past