I don't particularly agree with "willpower" -- I kind of think that sounds like some great super hero strength will come over us and take control. I think it's little steps and changes that have to occur that put us on the right track. I am constantly waiting for the "right moment" when "the stars align" and I can easily control myself and lose weight -- I think I decided today that is not going to happen (after I at allt he donuts, finished up a bowl of dip and pretzels) and now I feel like crap!!
When you feel like eating extra at dinner, call the game and get up from the table. I've even started scrapping all the leftovers into one big bowl before I leave the table, to stop me from finishing anything that makes it way back to the kitchen.
You can do this -- 100's of people on here have. Think of all the things in your life you've strived at and try to figure out how you made those happen.
There are going to be good and bad days, I'm just working toward having more good than bad
Good luck.