It’s a good idea to let the project sit for a bit between tracking and mixing to make sure you have everything in perspective. Sometimes tracks that are not “sitting right” to you as tracking wraps up sound just fine once you’ve had a chance to remove yourself from the situation. All you needed was a little perspective. The same holds true for a finished mix. When you’re finished mixing, set it aside and revisit it in a few days. You’re likely to hear things you missed the first time when you have a fresh set of ears.