If you can, don't master you own mix.
I mean, really.
Ideally (probably), the point of mastering should be to have a fresh set of ears and a completely fresh perspective listen to your mix and take out any little errors there MAY be there (if the mix is good enough, they won't have to do anything tedious!)
You could master you own mix, perhaps if it's months after you've last touched it. Or if you take a bunch of ruphies when you're done mixing! :D
But yeah. Get someone who knows at least a LITTLE bit of what they're doing (and who you know won't just slap shit on there to "make it sound better and louder"). Or let them do that, lmao, it's your mix, make it sound how you want to sound.