I have a journal / everyday book where I record probably way too much data: what I eat, where I go, when I sleep, what aches and pains or health issues I experience, where I drive, what I spend and how, what dreams I have, odd number sequences I notice, when where and how intensely I exercise, and really, another couple dozen intensely personal things that I started tracking because I wondered about the trends.<p>While I started tracking everything because I was hit with a bad migraine that came out of nowhere and I couldn't trace back to my normal triggers, I expanded what I track because I find the data incredibly fascinating and very handy to have. When I go to the doctor and he asks, "When did this start?" I can look it up. When the scale goes up, I know how many calories I've eaten, how much exercise I've had, how much sleep I've managed, and where most of my stressors are. A low protein diet can trigger depression, so I look for enough protein in my nominally vegetarian diet to make sure I'm getting enough, and adjust as needed.<p>I have a low-tech approach, but think about moving to a digital version so that I can integrate other data (fitbit data and sleep quality, in particular). The key to consistency is motivation. Once you've been doing it for a while, wow, not doing it is uncomfortable. Find something that works for you (phone app, moleskine, etc.), even if it's just an index card that you jot notes down to scan and OCR them later. Whatever you use, you have to have it with you at all times to be effective (which is why a phone app might work best for most people).