(figuratively) to strike while the iron is hot, to make hay while the sun shines

the more the merrier

to give credit where credit's due

the ball is in someone's court

(figuratively) to saw off the branch one is sitting on

once one has done something, one does not have to worry about it anymore (used to encourage someone to finish what they have to do)

in for a penny, in for a pound

revenge is a dish best served cold

One must strike while the iron is hot

Alternative form of il faut battre le fer pendant qu'il est chaud