To write sucessfully, you need to take into account how your reader is going to react at each stage of your essay. Although as the writer, you have an overview, or mental picture, of the text as a whole, your reader has to put together such a picture as they go along. The reader's experience of your essay is a process that happens through time, with the ability to understand your essay as a whole depending upon the reader's memory of what you're already said.
To make it easy for the reader to know where they are in your argument as they journey through your text, you need to give reminders of what you've already argued, and to flag up what is coming, an aspect of writing that is often called signposting. Doing this effectively depends upon the sense of the audience which you have formed (perhaps through tutors' feedback on previous essays) - an audience knows nothing at all about the subject of your essay will require more frequent and explicit signposting than one is more expert.
Reading is an ongoing process of creating the meaning of a text, and your job as a writer is to guide this creative reading process. Your sense of the audience will suggest possible responses to, or interpretations of your argument, and you need to show that you are aware of these by explicitly addressing them in your writing. This is particularly important when it is likely that your audience may disagree with the argument you're making, or have a different perspective on the problem.