Now that you've done the bulk of your research, you should have several pages (on the computer, on paper, or both) of point-form notes. In those notes should be full quotations you intend to use or paraphrase later, as well as general notes that you've already summarized or paraphrased. If you sit down to write the essay with this pile of unsorted stuff, inevitably you'll have trouble deciding where to begin and you'll keep leaving things out. It is much easier to group the notes, plan the essay, and then write, rather than trying to stick random bits in as you go