I know many microstock photographers became addicted to check
their stats. That is quite easy, being the numbers there at disposal. In the traditional agencies is not so, that's why there is this danger of becoming 'badly' addicted to check earnings in microstock.
One thing most people do is comparing month to month earnings. How many times in forums come out the topic of 'bad/good sale this month'? Bad thing to do! Really.
You cannot compare month to month, that is simply a measure of 'increase' (providing you have submitted at least a good amount of new good images).
The real statistic that count is to see improvement in portfolio efficicency, measured with sufficient data at disposal. That is: this year month compared to the same month in previous year(s).
Is consequent of my reasoning that is almost useless to follow day to day fluctuations. You can see in Yuri Arcus website a week pattern(that is the same for everybody, I'm pretty sure) that shows how Monday is slow start, Tue-Wed-Thu are the peak of the week, Friday start to decline and Saturday is usually the lowest. Sunday sometimes can be higher than Sat.
This to say that apart this pattern, instructive anyway, there is no reason to follow day to day earnings/sales, or do it just as a matter of curiosity and not as a reason to start wining or cry out that sales are down or celebrate sales up.
The success in microstock is built with years of hard work, not days or months. So measure of success is better made after one year not after one month or week.