As a human we like things loud. Your brain likes loud music. Turning music up loud is a great way to trick your brain into thinking the music you are listening to (or making) sounds better than it actually is.

It is best to produce at the lowest volume you can. That doesn't mean the lowest level to where the track is still audible. After increasing level past a certain point on your volume knob, you are simply amplifying sounds you can already hear just fine. You want to be around that point. (obviously, a good sounding mix at low levels is going to sound even better turned up)

I've seen TeeBee brag on twitter about the low levels he mixes at......