Is There a Best Practice for How Often to Check (or Not Check) Your Amazon Ranking?

As a newbie to indie publishing, I find it tempting to keep checking how many "units" of my book (as Kindle Direct Publishing calls an e-book purchase) have sold, but I'm trying to avoid doing this more than a few times a day. There are two main, probably obvious, reasons for trying to keep my sales-watching to a minimum:

1) Checking can become addictive, and like any addiction, it will leave me feeling dissatisfied and empty.
2) The time I spend checking could be invested in something more productive, like: actively marketing my books, writing a new book, exercise, spending time with friends and family--the list goes on and on.

On the other hand, checking at least once in a while has a purpose: to see which marketing techniques contribute to an uptick in sales.