Knock yourself out

[Justin Bieber]

Equivalent to Go for it

[Couch Potatoe]

A term for: Do whatever the hell you want, it doesnt bother me.

[Justin Bieber]

Same as go for it or go nuts.
If you really dont care at all about a person doing/taking something you say knock yourself out as in to do/eat until you pass out (if you really want to).
Same as go for it or go nuts.

[Tina]

to incapacitate or render oneself unconscious by means of physical, or mental, abuse or deprivation to ones own body.

[Mark Zuckerberg]

to work hard to achieve something, usually implying success