to "let go" of their former responsibilities, that they would now give to the sales manager. To give over what they had gracefully, and not make a big fuss over it. The analogy is to a hand which is grasping at something too tightly.
My girlfriend dumped me. I had to "let go" of the relationship.
My car broke down five times. It was time to "let go".
After years of practice, I still can't play the harpsichord. It's time to let go.