Excellent thread - give yourselfs a round of applause. 
I like my applause with a little bit of sugar and a little bit of cinnamon. Oh, and you have to use the right appls or the ause just won’t taste right.
Nitpick: the plural form is “yourselves” (and “ourselves” and “themselves”).
Why it’s possessive case sometimes (myself, thyself, ourselves and yourselves), and objective case sometimes (himself, themself* and themselves), I don’t know. But with “herself” and “itself”, it could be either case.
- “Themself” is for when you are using singular “they”, e.g., “Each student should solve the problem by themself.” But that’s a whole 'nother debate
This phenomenon is known as hypercorrection. You see it with who/whom, too.