Nowadays with the technology that we experience in DAW's (digital audio work stations) we tend to be attracted to staring at the big show of colored wave forms, super accurate meters, graphs and digital moving plug-ins that are music programs have to offer. Even know all the glitz and glimmer do serve as a purpose, we tend to forget that our ears are what is hearing the music not are eyes.
When we use both our ears and our eyes, our brains are taking in two different types of information at the same time in-turn distorting or weakening the signal of what we hear. And even know the numbers on the computer screen may never lie they don't always make the sound we are looking for.
One thing that any good engineer needs to do is turn off the computer screen or at least close your eyes when the sound that you are trying to mix is playing. You can try other things to get away from the computer screen as well, such as getting up and walking to the back of the room or to gain a different sound perspective you can walk from one side of the room to the other. You can also try letting the sound source play while you walk out of the room for a minute then come back into the room while it's still playing to see if you can pick up anything that needs to be changed.
One last tip, something I do often that a lot of engineers won't do is if I'm pretty close to being finished, I take the music and make a quick copy of it, then I take that copy to my car and ride around the block and listen to it; or I will take it to another room lay on the coach and set back and listen to it. A different room will give you a different atmosphere, and that might just give you a different perspective, then you can head back into the lab make some changes and finish up.