take the plunge
US /teɪk ðə plʌndʒ/
UK /teɪk ðə plʌndʒ/

1.
to decide to do something important or difficult that you have been thinking about for a long time
:
•
After years of deliberation, they finally decided to take the plunge and buy a house.
•
She was nervous, but she knew it was time to take the plunge and start her own business.