Rehearsals. For any musician that plays with other musicians, rehearsals are part of the routine. They are like the meetings you attend at work, but significantly more fun.
In an ideal music rehearsal, everyone attending will arrive ready to rehearse. Readiness indicates that the musician spent time to prepare alone: looking over the music, noting any trouble spots, preparing their instrument, and so on.
There is also a different mindset present when someone comes ready to rehearse. Mentally, they are focused on the task at hand. They are more engaged throughout the rehearsal, which comes after taking the time to prepare.
I’ve been in a lot of rehearsals. Some of them were fantastic; everyone arrived fully prepared to play. When that happens, the rehearsal is easier, more fun, and more rewarding. Sure, the music might be difficult, but the experience is incredibly enjoyable.
Some rehearsals, though, were essentially a train wreck. No one was ready to play the music. No one prepared beforehand to rehearse with the group. And no one was mentally ready to play. Instead of arriving with decisions made, everyone was trying to make decisions on the spot. And that is almost always a recipe for disaster.
This same truth applies to the teams that you lead: everyone must spend time privately preparing for the job they will do with the team. You cannot show up to a meeting, for example, and expect a great outcome when you did not arrive prepared. You cannot expect a project to be successful if you are not spending time alone to make sure your part is ready.
If you want to produce great work, just as musicians want to produce beautiful music, then you must work hard privately. You will never be on or lead a great team if you and your team members are not working hard privately. What you do in private will always impact what happens in public.