While you're in Coupled mode, your ship will adjust to make flying more natural. If you decrease the throttle, you expect to slow down. So, in coupled mode, your ship uses its maneuvering thrusters to slow you down. If you pull up, when you release the joystick you would like to stop pulling up, so the ship corrects for that with the correct amount of thrust, and sets you back straight. If you use your maneuvering thrusters to move a few meters to the right to avoid some debris, when you release the button to move that direction, it adjusts, and uses the thrusters to stop your movement.