I have a set of five core principles that drive my project management/ management philosophy. I've had them for many years, even predating my adoption of agile.
They are:
People, not projects: If you focus on the team, the team will do better. Better team, is a better product. I spend every day of my job trying to make myself obsolete by enabling the team and helping them grow.
Communication is 100% of your job: PMI says communication makes up about 80% of a PMs job. I call it 100% and the big thing is you have to be adding value. As a PM you are the ultimate translation point for the project. It's your job to facilitate all the communication and enhance it along the way.
Process is a Tool, not a roadblock (sub-concept: There is no, one right way): Don't ever let process take control of your project. If a process does not contribute value to the end user/ end goal, then look at getting rid of it. And if something has to be done, be open to if there is an easier way to do it. Inspect and Adapt.