The Wikipedia article offers a couple of classical and modern takes on the problem but I'd offer one more. That we misunderstand our own intentions. When I say “I’d like learn to speak Italian” that’s not what I mean at all. What I mean is “I’d like to be able to speak Italian.” and I haven’t even considered the work involved.
In my case it's carrying too much weight around. Even though I know objectively how much better it feels to be lighter, how much better I feel all around. I want to be thinner, and I want that even at the exact moment I'm eating something while I'm not actually hungry. I tell myself "You ought not to be doing this." as I actually put it in my mouth.
So I end up asking myself repeatedly WTF, why am I sabotaging myself even in spite of conscious recognition that this is exactly what I am doing.
Because as you say, I know I want to be lighter. I didn't say anything about wanting to eat less. You're a genius, thanks for giving me a new way to think about this. Even if it doesn't work.
Off to the fridge... (I kid, I kid... or do I)
I find that often helps me. It's being in the habit of reminding myself I have more than one choice when dopamine cravings would otherwise cause me to forget.