You should do it! I just looked at mine and I've been keeping notes since June 2007, so earlier this year was 10 years. Hard to believe. I just set a calendar reminder and each sunday I jot down a few things from the week. It really forces me to look back and reflect on the week and helps everything seem like less of a blur. I'd just write what happened at work, or health/fitness updates, what I was listening to or watching, how my relationships were going, that kind of stuff.
Anyway I'd highly recommend it, it's not only cathartic in the moment but it's also a lot of fun to be able to look back on ten years of it. What a different person I was 10 years ago!