he who hesitates is lost

(proverb) if you delay, it could end in a disaster

Example Sentences:

A: Did you get Radiohead tickets? The concert is tomorrow.
B: No!
A: They’re your favourite band, why not?
B: Because I waited until today to try and get the tickets. I’m so stupid!
A: He who hesitates is lost!

When Mark and Shane went to buy a used car, they decided to think about the purchase. When they returned, the car had already been sold. He who hesitates is lost.

From the Blogs:

Enhancing Sales -- He who hesitates is lost

Media:

Similar idioms:

1. you bet your ass
2. book in advance
3. bide one’s time