Observing and understanding various metering types to gain information. Mastering being the last stage of the creative process means quality control is imperative.
Understanding how every move I make will change the listener's emotional response to the track. And finding the best combination of processing units to achieve the most profound emotional response from the listener.
Ensuring every elemnt of the track can be heard clearly and in balance, through any playback system is a difficult challenge, but one I rise to with every job. Translatability is key.
While almost any loudness can be achieved nowadays, it is not my main priority - unless it is made clear to me that its a priority for you. It is becoming increasingly known that most streaming platorms now have fairly complex backends, that are pimarily designed for loudness management accross all tracks on their platform. I translate this into my practice, as having more freedom to make the track sound as good rather than as loud as possible.