Busyness describes how many meetings or engagements a person has in their schedule. The more meetings, the busier.
Effectivess describes how influential and impactful a person is in their tasks. The more value-add, the more effective.
I think there is an inverse relationship between busyness and effectiveness.
At a certain point, when your schedule becomes too full, you no longer can devote sufficient time to think carefully about issues, and your effectiveness decreases.
At the same time, there is a point where cancelling an extra meeting does not improve effectiveness. And perhaps we all need a little stress, anxiety, and pressure to step up and deliver our best work.
In general, effectiveness increases modestly with busyness, up to a plateau, then decreases dramatically.
If you agree with this line of thinking, then where is your plateau? What is the right balance of having things in your schedule and doing those things well?