Mastering is kicking my ass

Same old story, sounds good on everything except for the car. I've tried everything people have giving me. I listen to my car then go back. Doesn't work. I manually master. Doesn't work. I use the FL auto master. Still doesn't work. Also when I do somewhat make the car version sound it dulls the entire track on everything else. I am so close to calling it quits on this whole music production thing. It's been like this for 5 fucking months. Ima bout to crash out man.