Since I'll take any excuse to listen to a good song:
Indie authors are often advised not to check their sales rankings every day but to focus on getting their next book out. Since building a career is a long-term project, this makes sense. After all, very few of us are going to make a living from one book, and it takes time to develop a fanbase. So why is it so tempting to visit Amazon and Smashwords and ACX every day, sometimes more frequently?
I think perhaps it is the intermittent nature of sales that makes checking rankings so addicting, at least in the beginning. In fact, the random frequency of receiving rewards or sales makes it harder to break the habit of checking sales. Does that mean you're in trouble if you've already established this habit? I think it depends on how much it interferes with your writing. If you can manage to make the checks quick and do them at a time when you're not able to write, then it shouldn't be a problem. However, if you do it during your writing time or let yourself dwell on it, then checking sales is a distraction. Perhaps then it's time to find another way to motivate yourself either to write more or check less. For example, you can only check sales after meeting your daily quota, or only allow yourself to check sales when you're trying a new marketing technique.
Are you a ranking addict? How much are your emotions affected by your rankings? How often do you think an author should track sales?