It helps to remember that the downvote button is so close to the upvote button that it’s very easy to hit it by mistake on mobile. And I reckon most people don’t take the time to double check and undo the downvote.
I feel you, and it’s a natural worry. I deal with it too. But remember, the point of HN is for the discussion to be for the readers. And reading about downvotes is boring.
One hint that helps me, is when I write things like “Smart people don’t like statistics?” —- it sort of helps me realize that I’m in the frame of mind where I should step back and close orange website for awhile. And I mean all of this genuinely; I’m not patronizing or just saying it. It happens a lot.