Some of the worst fights my husband of 33 years and I have had were over this same issue. I could never just buy some treats and have one when I wanted it......he'd eat his portion, and then he'd eat mine too. But food is only a symbol of a much bigger problem, and that is RESPECT---I felt disrespected when he told me he'd leave my food alone and then eat it when he was out of whatever treats he had. Eventually he got the idea, and now he leaves my stuff alone (and as a reward, I usually wind up giving it to him).

Fortunately, he's never accused me of "acting bipolar" when I get after him about something. Sometimes he'll ask me if I've taken my meds, which offends me a little because I believe I am allowed to have NORMAL emotions. But otherwise, he's pretty good about the whole mess, and he often has some really good insight from years of dealing with me.