Another tidbit I wanted to throw out there.
Always use multiple methods of listening when checking your mastering.
Listen to it with your studio monitors, studio cans (headphones), generic ear buds, bookshelf speakers, Bluetooth speaker, and lastly check your master how it sounds mixed down to mono.
A master mix can sound great through one medium and terrible through another.
Not everyone is going to listen to your stuff through the same quality or type of playback medium.
Other thing that can be rough is making a mix that sounds good stereo and mono, a lot of portable Bluetooth speakers are just summed mono and are a widely used playback medium.
I’m no pro studio engineer, most of my experience is in live audio, but I’ve been dabbling at home with Ableton and Logic Pro. So far my biggest struggle has been making something sound good mixed in stereo when played back mono. Going too crazy with stereo panning effects and automation panning has lead to some serious phase cancellations when stereo mix is summed to mono.
Cheers.