i cut my own slack - A bragging way of saying no one else is worth your time, and

A bragging way of saying no one else is worth your time, and you're the only one who can help you, so you just do it yourself.

I cut my own slack. You're still trying to get your friend to help you, and I already finished my work and ate my snack.

I cut my own slack. You're still waiting for the game to start, and I already finished my homework and got my candy.

I cut my own slack. You're still fighting with your sister, and I already finished my math and had my lunch.