Oh, Ye of Little Faith (or Trust)!

Dear Mrs. Ditter, I am staying with a friend who has invited me to help myself in her kitchen. Sitting on her counter is an unopened, Costco-sized box of my very favorite forbidden fruit: sesame snacks.  It's been unopened all week and I can hardly contain myself.  Should I take her at her word and help myself (I haven't had the guts to ask about these specifically), resign myself to abstinence, or wait up until she gets home tonight and beg?  And how seriously, really, can I take someone when they say, "Help yourself"?  I know I don't really mean it and am always shocked when someone eats the last of the chocolate, for instance...
Yours, Sesame Snack Deprived
Ooh, I like these two questions, the first one so specific, the second one so general. I also like those sesame snacks, and I cannot believe you've let the box stay closed this long. I would have asked her specifically about the sesame snacks while ripping open the box. However, I'm willing to bet that you go home at the end of your stay without having eaten a single one of those luscious, crunchy, sweet, snappy little sesame treats. Mmm. What you missed!
Let's look at your real question, though, which is "How seriously can we take people when they speak to us? How deeply can we trust the words that come out of their mouths?"

I think this varies for each of us. I also think you've answered that question, for yourself, anyway, in your very next sentence: You don't really mean it when you say "Help yourself." And so it's no surprise that you can't trust that anyone else really means it.
I grant you that finishing off the last of the 62% dark chocolate is somehow much different than making yourself a bowl of oatmeal, even though in a perfect world, both instances would be covered.
In general, I think we need to behave in other people's houses the way we would want them to behave in ours. So, because you "don't really mean it" when you tell other people to help themselves in your kitchen, it seems that you should tread lightly in your friend's kitchen, for your own peace of mind if for no other reason.
Just a thought: This second question obviously leads into a whole other discussion about how much can you trust people--not just in what they say about how you can behave in their house--but I'll just let you reflect on that on your own. Let me know if you have any epiphanies, or even small glimpses. For some reason, I think if you sit with this, you'll feel a little loosening up around this issue: Either you won't say "Help yourself to anything" if you don't mean it, or you'll find that you can say it and mean it. 
Now go home and buy yourself some sesame snacks. Bon Appetit!
Questions for Mrs. Ditter? Leave them in the Comments section, below. And as always--thanks for reading.