Most won't experience this as solo artists, but sometimes when making music, sacrifices must be made to certain elements in the track. To either get them more themed to the choice of style you're attempting to recreate. E.g a sound, a riff, a snare choice, a vocal etc these are just some of the things that are hard to get right in each track. For these reasons I encourage people to form groups, as it takes a lot of the 'should this be in the track or not' hesitation out. When you get to a stage in a track where you begin to over analyse something and start over-processing things, it really helps to get a second or third opinion. Saying that sometimes it works against you and you miss a certain element to a track that was once there. But 90% of the time its for the best. And on a personal tip it helps you finish a track much quicker than on your own imo. Thoughts?