[Mark McLeod]

Use the Set Output from the same motor palette and wire in a zero.

Any motor that might possibly have been moving at the moment when the robot was Disable should be set to neutral.
The reason is that you might come out of the Disabled state doing something different than when you entered Disabled, e.g., switch to Autonomous from Teleop, or switch to Teleop from Autonomous, or restart Autonomous.
If Teleop last had an arm motor moving up when you disabled, then if you don't set it to neutral in Disabled.vi and switch over to test autonomous, but autonomous doesn't use the arm until later, the arm will immediately continue moving upwards on it's own. The motor will continue executing the last output it was told.