I am a big believer in outlining. I outline almost every document that I write. I have had an outline that was over 20 pages long. It was for a novel that I was writing. I went back and reviewed my outline, only to find out that I had not been following the outline. That was okay. It happens like that sometimes.
Outlining, mapping a piece of writing, or drawing a diagram of a document is a great way to keep on task. It may not be a formal outline, but even having a list will help you stay on track.
One thing I recommend when doing an outline for a research paper is to place quotes or a numbering system for your quotes in your outline. This will prevent you from having to search for your quotes once you start writing your paper.
A last thought about outlines… It can help you break up your writing (long essays in particular) into sections. By breaking up a long essay into smaller sections, it will make the writing seem less fearful.