Here are a few thins you can try to create really improve your mixes.
Always remember to take a break, leave a gap to breathe, to think and re-evaluate, this will save you time and frustration in the end. To compare is sometimes good, make it a habit to check other mixes, professionally mixed ones may provide you a guide to better your mix. Consider your delivery, it’s not the loudest sound that brings the best mix. Test and test and test again. Try taking the recording into the car with you and listen with a notepad (or Evernote, etc.) and get really critical with where a sound pokes out or sounds bad. A lyric sheet can help you here. Then take the notes to the studio, make changes, and listen again.
Read more here: http://www.musictech.net/2015/02/twenty-mastering-tips/