I play it through my car stereo, record it through my cell phone voice recorder - and then play it back through headphones.  
 
man i suck.

My Mixes Sound Better When....

 
.....the volume is at 0.

I find the best place to listen to my songs is in the bathroom. In the basement, in my neighbors house. 
 
(edit- that's with the playback system in my house, in the attic with all the doors and windows shut and someone cutting the lawn helps too... when I listen to them like that, they compare perfectly with every other well known hit record and artist .  

Some people are re-recording mixes into 1/4" cassette decks because they love what it does. What it does, of course, is limit dynamic range and impose a nonlinear frequency response, adds masking noise via tape hiss and frequency modulation from flutter. If you were to play it back through a car stereo and record it with your smartphone it would do some of the same things, most notably the compression part.
 
I am disappointed in everything I mix. I'd guess the vast majority of mixers, both professional and amateur, are at least somewhat disappointed in their own work. The inescapable conundrum is that the better you get, the more critical you become. Dunning-Kruger aside, I don't know anyone who's genuinely proficient AND has reached a point where they genuinely believe everything they do is golden. 

I tweak things, add some new thing, export it, convert it to mp3, and send it off to my singer/songwriter/performer buddy. He gets the email and instead of making a cd and putting it on a decent stereo, he plays it on his crap computer speakers. He NEVER describes the mix as I have so diligently prepared it. Too much bass, and no clarity 2nd vocal too loud(I turned it down!). He takes it out to his car, and it sounds fine....... He will never learn!

bitflipper
Some people are re-recording mixes into 1/4" cassette decks because they love what it does. What it does, of course, is limit dynamic range and impose a nonlinear frequency response, adds masking noise via tape hiss and frequency modulation from flutter. If you were to play it back through a car stereo and record it with your smartphone it would do some of the same things, most notably the compression part.
 
I am disappointed in everything I mix. I'd guess the vast majority of mixers, both professional and amateur, are at least somewhat disappointed in their own work. The inescapable conundrum is that the better you get, the more critical you become. Dunning-Kruger aside, I don't know anyone who's genuinely proficient AND has reached a point where they genuinely believe everything they do is golden. 

I'm at the corroded rust stage. At my age I'm not likely to EVER get to aluminum let alone golden.

bitflipper
I don't know anyone who's genuinely proficient AND has reached a point where they genuinely believe everything they do is golden. 

 
Have you ever worked in Hollywood?

When I set the proper track volumes and simple EQ, then mix it down and leave it alone.