Via BoingBoing I found a Lifehacker post about a nifty vocabulary tool called "Wheel of Feelings," which is being widely attributed to a teacher named Kaitlin Robb. The link back to her (I assume) WordPress site requires a WordPress login, and I don't have that, so if you want to dig further, that's up to you.
It's an interesting idea. Accurately describing feelings is often hard for us when we're talking about ourselves. And it can be hard for writers, too. It's important to change-up the words you use from time-to-time, too. Describing a character as "sad" over and over isn't as good as switching to some more specific versions of that emotion: lonely, bored, vulnerable, powerless...
Now... I know your first instinct as a reader and writer may be to say, "Wait a sec... 'powerless' isn't a synonym for 'sadness.'" You are correct. But we're not talking about saying the same thing differently, we're talking about saying slightly different things. Why is your character sad? Is he lonely? Is she feeling small and insignificant? It's better to explore the more precise terminology, even from a "just thinking about it" perspective. You may not go with one of the more detailed words... but it never hurts to probe your characters' motivations -- and your own -- using easy cognitive/writing tools.
I do not suggest that the groupings in this tool are the only or best ones; just that it's an interesting and potentially useful tool.
From a readability standpoint, I much prefer a grid to circular text tools, though, and colors can help differentiate choices, so here's my take, "The Grid of Feelings."
Also, wheels should spin. So I created an animated GIF version. If you want to find out how you're randomly feeling, load it up into a browser or tool that will let you pause GIFs with the ESC key (Chrome will not).
Note: My thanks to Kaitlin Robb. I could not get into the Wordpress site connected above. If she (you) is (are) the creator of the tool and object(s) in any way to this use, please let me know and I'll take it down. I believe that it is transformative enough to qualify as a fair use, but that's the minimum standard and "not pissing off people who provided a useful idea" is more of what I'm in favor of.