This is what it all comes down to. It's like saying no to drugs. It's easy if that's the way you are put together, and it can be incredibly hard if you are not. I am always hungry, sometimes even when I've finished a meal. When I was working I would eat lunch with thin/normal size friends, and they would get about half what I would get, and not finish it. I, on the other hand, would only not get more out of embarrassment. I don't know if it's physical or psychological or what, but if I wasn't always hungry I'd be much thinner. I know it's possible to overcome with extreme application of willpower, but it's very hard, and even if I lose weight it's very difficult to keep it off. I've tried many of the diets and not a one of them has ever dealt with the hunger issue.
And I actually eat quite healthily, most of the time. I love veggies, I haven't had a sugary soda in decades, I don't eat too many processed carbs. I just eat a lot. When I quit drinking alcohol I lose some weight, about 7-10 lbs. That's an easy fix. But it's the food that's the hard part. If there was a drug (other than meth or coke) that would stop my hunger I'd probably lose 50 lbs in a year.
How much exercise do you get?
Do drink enough water?
My wife is quite fit, and to be honest, it upsets her when heavier people assume it's "easy" for her. It isn't. It requires a lot of effort, at times when frankly, she'd rather not put that effort forth. Sometimes it requires not eating something that at that moment, she'd rather eat.
When I quit smoking it wasn't easy. I substituted water and exercise, every time I wanted a smoke. You might try something like that to get you started.
Good luck!