Just a thought on blogging motivation: It seems that once you decide that you'll make money form your blog you realize that you then have to get as much targeted traffic as possible. To do that you have to keep adding lots of relevant content. Of course you can never do enough!
That presents a problem because you can start to feel guilty if you're not adding posts at a high enough frequency. It also means that the quality of what you're adding might drop somewhat, since you're valuing quantity over quality.
That's why I think it's important to keep recalling why you started in the first place (that is, for enjoyment!), ease up a little and just work when you feel like it.