One more thing that I figured would be mentioned by now (or maybe I missed it) is if you are stuck using headphones most of the time (like I am) and/or cannot afford proper monitors just yet you may want to look into a device by Focusrite called the "VRM Box".
It's basically a little device with bundled software that emulates different monitors, soundsystems and environments through your headphones. There is a "Pro" studio environment with common pro monitor emulations, a "Living Room" environment with different stereo system emus and a flatscreen TV emu. And there's a "Bedroom" environment with some of the smaller pro and consumer emus as well as computer speakers and whatnot.
It's not perfect of course and doesn't replace a properly treated room and/or proper monitors but it does provide a bunch of alternative and reasonably accurate sound sources and common listening environments. I've have been getting much better mix results since I started using it to comb through all the settings and finding bad spots in miy mixes. I combine that with my pure headphone sound, my monitors (which are good but in a bad room and I can't crank them) and all the other sound sources I have like a bunch of consumer headphones, two stereo systems and whatnot.
Bonus is that it acts as an audio interface too if you need it to. No inputs and just the stereo headphone out but it's perfect for just writing MIDI, editing or mixing through. It's super small and uses USB for power and audio when it's being used as the main interface so it's portable.
It's also got a big, slick and smooth volume knob on it so it can be used as a "Big Knob" for volume if nothing else (you can hook it up as a kind of a slave to your main interface via SPDIF... in fact that's how I use it). A good studio volume control costs almost or as much as one of these things (about $100).
Anyway, I don't work for Focusrite. Just very happy I bought this thing. It's been immensely useful and sounds like it could be just what you need while you sort out all the other suggestions made here.
Cheers and good luck.