Certainly one has to still watch the diet even after surgery. The sleeve is a tool, not the cure. That being said, although my head tells me I am hungry, I can't eat much. So the intake is restricted. But you still have to moderate your diet some and watch what you eat. I have seen some cases where some weight has returned. So far for me I am steady (maybe fluctuate 2-3 pounds or so, up & down). Seems after 1 year the loss part is pretty much over. Now in maintenance.
Like i said, for now don't stress. Get past the surgery, recover and then follow your instructions.