Now, you could just satisfy your reader's expectations. You might show that the object you have studied behaves exactly like the theory says it should. But this does not teach us anything new. You might also disappoint your reader radically by saying that the object is nothing like the theory says. But this is really just likely to draw your results into question; the reader has more invested in the theory than in your results, remember.
Suppose you're writing a paper in ethics. You will present the reader with your theory of justice, which the reader will presumably share. You will then present the results of an inquiry into a particular set of social practices. The theory of justice tells us what the "right" thing to do would be. Now, there are a number of possible interestingly disappointing results. You might show that the practitioners adhere to the principles in your theory (that their practices are "just" in that sense) but that their actions nonetheless have negative consequences. This would be disappointing because it means that being just does not mean doing good. You might, conversely, show that the practitioners do not adhere to the theory, but that this has perfectly "just" consequences in practice. Again, this would reveal that our theoretical expectations about the relationship between particular norms and particular social outcomes require some adjustment.
There are other ways to disappoint your reader, of course. You might get the reader to expect that the people you are studying are "good" (this would be done in the background section) and then show that they fail to follow the generally accepted norms (presented in the theory section). But in all cases the trick, the "art", is to make the disappointment instructive, not merely depressing. You don't want to argue that our ideas about justice are simply wrong or that real life is simply unjust. You want to the reveal the flaws in existence that we can do something about.
In Denmark, many of us are looking forward to the Easter break. If you're taking the whole week off, here's a little bit of advice. Make a clear plan for the first few days after you get back. In particular, decide already before you go away what you will do during your first writing session back. Be specific. Don't say you'll "get back into it". Decide exactly what section you start working on. Decide on the first paragraph you'll write when you get back.