You’re the only person who’s been there for every chapter of your life. Be decent to them.

Everyone else joins your life partway through and leaves at some point. You are the one who was present for all of it, including the parts nobody else saw, and you are also the voice commenting on it all day. That makes unkindness there different, because you cannot walk away from it at the end of the evening.

Catch one sentence you said to yourself today and ask whether you would say it to a friend. If the answer is no, you have found something worth changing, and changing it is mostly repetition. Start with the tone rather than the content. Same facts, a voice you would actually listen to.