I've often felt that there were tons of similarities between mixing music and cooking. I'd probably see more similarities if I could create meals in the kitchen that didn't involve a bag of some kind or a jar of peanut butter. But I get the concept.
One of the similarities that comes up a lot is how one thing can mask or overpower another thing. The best chefs use multiple flavors that complement each other. And if one ingredient is not as prominent as it should be, the right answer may not always be to "add more." Sometimes a flavor can be coaxed out more by doing something with the heat, or adding a touch of another thing that makes the first thing stand out more.
If you followed any of that, you may sense where I'm going with this. In a music mix, if the acoustic guitar seems like it can't be heard well enough, the amateur will immediately turn up the volume on the acoustic guitar channel. But the master will know to try more subtle moves, like maybe turning down just the middle frequencies of the piano - not the entire piano track, but maybe just a few key frequencies of the piano that may be masking the guitar (you'd use an equalizer [EQ] for this). Other things to try would be to use reverb to push something more to the back of a mix, or to use panning to help separate certain sounds.
The track volume (gain) sliders are like hammers. Beginners see them as the only tool for mixing, so every instrument is like a nail. Did I go awry with this simile? Eh, you get the idea.
Here is an article by Joe Gilder that uses this extended analogy to provide some tips on bringing focus to a music mix.
The full article is here: http://www.prosoundweb.com/article/in_the_studio_three_ways_to_find_focus_in_a_mix/