The thing is a lot of people do not understand what mastering is...
It's not just turning all of your gears and tweak here and there....
absolutely not!
sometimes mastering is just critical listening and simply approve great mix
that's it;
mastering yourself in the very same room the mix was done on the very same monitors is actually contradiction to mastering process...
main thing about it is a 'third party fresh pair of ears' in properly treated room with great monitoring...
tweaking knobs is just a small part of it, and it's not a necessity


good luck anyway!