Obsessing over sales rankings

I don't know about any other authors, but I'm somewhat obsessed with the sales rankings of my book on both Amazon and Barnes and Noble.com. I find myself looking at it at least twice a day, I guess because I bored or something. I watch how, at least on Amazon, my sales ranking goes up to a few thousand(around 100,000) and for a few days sinks into the millions, then out of the blue, jumps all the way up to like 80,000 or so. BN.com doesn't seem to fluctuate as much as Amazon, I don't know if their sales figures are more accurate or they have a different way of calculating the rankings.  I'm sure I'll find out once Iuniverse posts what I sold in March in the next few days, which I'm am definitely looking forward to since I set a very modest goal of 100 sales. Anyway, I was searching for a way to watch the figures and stumbled on rankforest.com, which keeps track of figures from both websites. I added my book and I watch the graph go up and down throughout the week, which is cool or not, depending on your mood at the time.  I don't know how Out of Time compares to other book sales because I really don't want to get discouraged. I just wonder if authors like Stephen King or James Patterson ever obsess over sales anymore or now that they're rich they don't have to or need to?