When you start documenting how you spend your 168 hours, you'll notice things. Here's a quick change I made.
I've long been interested in writing fiction, and one way of getting better at a craft is to read, critically, how other people practice that craft. But when I documented my 168 hours the first time, I noticed that I was spending pretty much zero time reading fiction. It wasn't that I didn't have time. I don't have much time, but I have drips and drabs here and there, and you can certainly get a few pages read in 30 minutes. The problem is that I often spent those spare minutes checking email, surfing the web, or reading short magazine articles on how to walk off the weight.
In order to fill your time with a new habit, you have to make it easy – so now I have fiction around that I do want to read. Then you just have to commit to do it. When a spare hour arrives, I try to seize it and pick up a book. Net result, when I kept the time diary a second time, I actually did have about 2-3 hours of fiction reading in my week. Will it make me a better writer? I don't know, but it probably doesn't hurt.