Kindness is not an inherent personality trait. To struggle, to love, and to be kind are active states of being. You have to go against much social conditioning to be kind. Its a choice. Make the choice to be kind.
But also, be reasonable.
You're not going to love the hate out of a Nazi.
Choose to be kind but understand not everyone is worthy of your kindness. This is being kind to yourself. You deserve kindness, too.