Since a standard journal article has 40 paragraphs I've fallen into the habit, when talking to my authors, of referring matter-of-factly to "paragraph thirty-nine", i.e., the penultimate paragraph of the paper. It is also the first paragraph of the conclusion.* It serves a very special function in the paper and is worth giving extra consideration.
You construct the key sentence of paragraph 39 by a simple procedure. Take the key sentence of paragraph 3, the one that begins, "This paper shows that...", and simply remove those first four words. That is, if the key sentence of paragraph 3 is "This paper shows that the financial crisis was caused by the performative effects of organization theory" then the key sentence of paragraph 39 is "The financial crisis was caused by the performative effects of organization theory." Notice that despite their similarities, these two sentences make very different claims. The second (§39) tells us something about the financial crisis; the first (§3) tells us something about your paper. Paragraph 3 will therefore provide a description of your paper to support your claim that it will show us something. Paragraph 39, however, will provide a description of the financial crisis to support the claim that it was caused by organization theory.
Like any other paragraph in the paper, you have around six sentences and no more than 200 words at your disposal. Remember your reader. At this point your reader has listened to everything you have said. Your reader knows what your key terms are and has read your entire analysis. Your reader knows what methods you have used to gather your data. Your reader has also been informed about relevant background details. Your reader even knows what implications you have drawn. That means you can expect a great deal of your reader in making sense of this paragraph. You can give it to the reader straight.
Paragraph 39 is not an abstract. An abstract merely describes an argument, and therefore looks more like paragraph 3 than paragraph 39. Paragraph 39 actually makes the argument. It is the part of the paper that expresses your major claim and adduces the strongest evidence you have for it. The strength of that evidence, of course, depends on the strength of the rest of your paper—mainly, the analysis section—but that's the thing I'm trying to emphasize: Your reader has already read the rest of your paper. You are therefore entitled to presume that your argument is strong. This is the paragraph where you state your conclusion and tell the reader, without blushing, why you think it is true.
For perhaps obvious reasons you do well to rewrite this paragraph several times. It is the statement of your ideas that the rest of the paper is putting you in a position to make. Getting clear about what it will say will therefore also help you write the rest of the paper.
Update at 3:36 pm. In my original post, I had mistaken written "the first paragraph of the introduction" here instead of "the first paragraph of the conclusion". Thanks to Jonathan for pointing it out.