go for it

verb3

1. •
   To put maximum effort into achieving something.

   • To win the competition he has to beat his personal best, and he's going for it.
   • He really went for it.
2. •
   Used to grant permission for or to give endorsement of a suggestion or proposal.

   • May I use your bathroom? ― Go for it!
3. •
   To decide to do something; especially after a period of hesitation.

   • His phone was off so I couldn't ask his permission, so I decided to just go for it.