My brain can work both ways, depending on what it is I want, how strongly I want it, and what the reasons against it are.
For instance, going with the chocolate example, if wanting to lose weight is the only reason to not get the chocolate, yes, I'll still want it but I might (I hope?) refrain. But if I'm trying to lose weight AND it's expensive, or it's good chocolate but not THAT good, then those other reasons will add enough to make me not even want the chocolate anymore.
Deciding to have sex with someone will of course have even more complications. Do I want to have sex with them in a, "They're hot, and from what I hear it'd be fun!" kind of way, or do I want to have sex with them to express deep feelings for them? How strong are the reasons against? Is someone not 100% comfortable with it or is there evidence that I'd be (literally) fucking crazy? The answers to those questions and more would determine if I still want to but don't do anything or if I stop wanting them completely.
Pan Female, Hinge in a V between my mono (straight) husband, Monochrome and my poly (pan) partner, ThatGuyInBlack