In my salad days, I would have replied: keep an accurate, comprehensive diary; take a lot of photographs; and hang on to all your receipts. Now I know better. None of this solves the logical problem. For example, when you are writing down your thoughts or acts in your diary, are you remembering correctly and hence describing correctly what you thought or what happened? When you later look at the photographs you took during your trip to Mali, how can you be sure [memory?] that these were the images you took there? There is nothing in the image itself that reliably testifies to its own veracity. [No memory-image verifies itself.] The label on your jeans says "Levi" [i.e., not a fake made in Bogalusa], but is there a label attached to the label that says "That other label is genuine, and tells the truth"? Even if there were such a label.... [No label verifies itself.] When God says to you, "I AM THE LORD YOUR GOD," go ahead, be brave, and reply, "Oh yeah? Sez who?" "ASK MY WIFE, YOU DIMWIT." (Jean-Paul Sartre & Bill Cosby.) As I said, the logical problem remains. But the practical problem is solved by diaries, images, and, especially, receipts. You can keep a list of all your wives and lovers (make sure you define "lover" fairly); you can take photographs of all the places you visit, and of all your belongings, and even, page-by-page, of your diary of wives and lovers; and you can buy brown/green accordion-style multifiles and store your receipts alphabetically or chronologically. But make copies of everything, i.e., back up your life. You might not fear the reaper, but watch out for the IRS. Let us return to the logical problem: backing up your life, i.e., making several copies of everything and storing these copies in different places (in case one set gets destroyed, say, in a fire or earthquake) does nothing by way of increasing the veracity of the original. As Ludwig Wittgenstein said somewhere (unless my memory fails me), if the newspaper says that UCLA beat Florida, you don't buy another copy of the newspaper to make sure that UCLA beat Florida. You go online. (Even so, of course....) For more on memory and its problems, see question 150 at http://www.amherst.edu/askphilosophers/question/150.