Macros??

Currently, I have my macros set to the ratios that MFP set up when I first signed up - 55% Carbs, 30% Fat, and 15% Protein. I know that I'm definitely not getting enough protein, and I have a really hard time getting it up to that 15%, which I know is not good at all. I also want to decrease my body fat percentage, so that would mean lowering my fat percentage, right? So what should I set my macros to? Is there some rhyme or reason to how you chose yours? I have a basic idea that I should lower carbs and fat and increase protein, but I want to do something sustainable for me - obviously I intend to work harder on getting my protein, but I don't want to set it at something so high that I never reach it and it just becomes a pointless goal. Does anyone have any advice?