Definitely positive.
My genes will always be with me to give me that tendency to gain weight more than a 'naturally thin' person, so I'm in this for life, and I am NOT going to spend the rest of my life calling myself names and talking down to myself every time I happen to dare look at a slice of pizza. (Like this would ever stop, hehe.)
Granted, it took me years to manage to reach that state of mind, but drats, things are hard enough as they are, after all... no need to make it even harder on myself.
Besides, I'm like dogs, I do better with positive reinforcement than with negative remarks.