I have heights of self-kindness in me.

You have already proven this, just not in your own direction. Think of how you handled a friend at their worst — the patience that was available, the complete absence of scorekeeping, how obvious it seemed that they deserved some slack.

That capacity is installed and working; what it has is a routing problem. The redirect is unglamorous, and it happens mostly in the two seconds after you make a mistake, when the old voice starts up and you decide, this once, not to agree with it.