When mixing a track it can be incredibly useful to use a reference track. This simply means using another track which you admire and which shares similarities with your own track as a reference to how the mix could sound within your own music. Using a reference track helps to avoid ear fatigue, which will make your track sound better no matter what, when your ears become fatigued whilst mixing you will not be capable of hearing any changes that should be made and run the risk of adding too much to a mix also. When picking a reference track it should have a mix which you admire and which you can aspire to; there are also many other technical considerations when choosing a reference track, it should be in the same genre of your track, and have similar instrumentation so that you can listen out for certain mixing techniques which you could incorporate into your own mix. You should also take into consideration the sonic aesthetic of the track and whether it fits with your own music and is something you can aspire to hear within your own music. A reference track is not something to directly copy but something to help guide and inspire you, it should be a track you admire and hold a sound which you aspire to be able to reach. It is entirely possible to mix without using a reference but using one can be better and help you to work out your sound, you will be able to listen out for particular effects such as compression, distortion, EQ, etc, and how and they have been used effectively so you can emulate these techniques whilst also adding your own flair. It is important to find the balance when using a reference track of taking inspiration and direction whilst also maintaining your own creative control and flair. Overall using a reference track is a useful and common practice which can help make your mixing skills develop and help you to avoid the ear fatigue that comes with mixing the same track over a long period of time.