I actually tend to think best in first person singular. It is all about me. But then, if I am to give into the desire to thoroughly examine and interpret my experiences, it might be wise to back off and speak in the third person. It is near bed-time, and I was in the bathroom getting ready to brush my teeth. I heard the voice in my head saying, "Tonight he changed his regular habit of brushing his teeth first and started with flossing. Somewhere he had heard that it was better to floss first. So having first flossed, then brushing, he rinsed with the minty mouthwash and checked his teeth with his tongue for any remaining orts." I love the word ort. It means a scrap or remainder of food from a meanl. I find it amusing that this little word that is usually only found in crossword puzzles, so aptly describes those little bits from pork chops or peanuts. I digress.
Above when I was describing my observance of the voice in my head, I naturally used the third person. It was as if I were a scientist studying the human in his natural state. Detached and removed from the subject. And probably omniscient, which means I, as the writer, know all. I don't. So there you have it. The first person singular seems the best choice. Not only is it the best choice for writing a memoir, but I believe it is the best choice is living your life. Everything has to come from an I prospective because you only can speak authentically of your own feelings and opinions. Anything else leads to accusations of being judgmental or an a**hole.
"I am sure I am being way too cerebral here", he thought, hoping you, dear reader, would not think him too much a pompous windbag. Really, the most important thing here is to be authentic. To find your voice and write in it, speak in it and in general, think in it too. Whether it is he or me, it is my voice. And that, I realize, is what makes it imperative to choose the correct person to tell the story.