I just began quilting last spring. I keep notes in a marble notebook - basically instructions on how to make items. I have one page per item. I also photograph everything I make. It's amazing how fast you forget especially when you give them all away. My intention is to one day print all the pictures and put them on the page opposite the instructions. (I'm waiting to have 100 pictures to print because the cost per print drops significantly at that point.)
I've made myself the same purse a few times and I was very glad I could easily find the instructions. Same with my tote bags. I make a lot of them but still have to refer to my instructions for the best handle length etc.