For example, here is a pair of 6 word memoirs I made up for Harry Potter and Voldemort:
Friends—loyalty more powerful than magic.
Kill you first to live forever.
Perhaps this is just a fun little exercise, but maybe it can also teach you about what your character is willing to risk, or where the heart of your story lies. The core of several of my novels can be summed up something like this:
True magic is will over wand.
Even fool's courage sparks dragon fire.
Sun shines second star to sisters (accidental alliteration, I swear!).