I have a small notebook that I have used for actually, decades. I'm onto my second book now. I didn't really plan to use it as a diary, but it is a bit like that. I write down the date, what I am making and for who and measurements, colors and even diagrams. There are some things I make that I don't put into the book, and usually regret when I want to make it again! It is interesting to go back through it and read what I've written and made.
Try it and don't make it a chore. Make it a place to jot ideas, what worked and didn't work and your feelings. I even put in the weather sometimes!
geneva