Logic playback Sounds Different From Bounced .WAV .AIFF &.MP3's

I am usually pretty good at mastering. Maximizing my volume for just about any sample or song i produce. But this has had me stuck all day. Literally. And every time I do something to correct it, something else seems to get off or it just doesnt sound the like i heard it. And thats the big problem here.
What i hear in logic, no matter what i seem to do, (I can and have worked back on the forth on the mix and the mastering 100 times) And it just never replicates what I'm hearing. How are you suppose to produce if you cant rely on what you are hearing? I even start bouncing terrible sounding mix, just to see if it would be consistent and of course those are terrible. i don't understand what I'm doing wrong on this one. It has me baffled to the point Im going to give up on music, and life, and everything that was important to me. So someone please help.

J/k about the suicide, but still. PLEASE HELP!