You determine kindness's meaning. Kindness is how you choose to show it. Kindness can be empathy, acceptance, kind gestures, and thoughtfulness; the possibilities are entirely up to you.
We usually consider being kind towards others. Have we forgotten the one person who needs kindness to show kindness?
Imagine if self-care were a natural thing, the self-help section would disappear. There would be a large area in the book store to put more sofas.
Being kind to yourself no matter how miserable you feel should be easy. Give yourself a break once in a while, learn from your misery and be gentle when you feel down.