They tell you that ‘you’re so great at [thing]’ and you get flattered into doing it, whereas negging is when they criticize you so that you’ll chase their approval and do what they want.
One manipulates you by making you feel good about yourself as a method of getting you to do what they want, and one manipulates you by making you feel badly about yourself as a method of getting you to do what they want.
Unfortunately, you’re essentially chasing their approval – or centering it – regardless of the method.