Have a mastering contest! Mastering yourself is hard, because there’s always that nagging feeling that you didn’t quite get it right. When you hold a mastering contest, you have a chance to check your sanity by comparing your work to other masters of the same song. Ask a few mastering engineers for a free mastering sample.
Worst case scenario, they all sound worse than your master, which is actually a win! Now you know you did a great job!
Best case scenario, you hear a master that blows your mind and elevates your audio.
Having a mastering contest is all about taking advantage of the fact that many mastering engineers offer a free mastering sample of their work. It’s awesome. It’s free. There’s no downside.