Outside of medication, what sorts of things do people do to prevent and/or cope with intrusive thought problems?

My latest one is that whenever I have to walk down a flight of stairs, I imagine myself falling and terrible things happening. I physically tense up and feel anxious, and have to move down the stairs very slowly and awkwardly. I live in a three story structure at the moment, so I deal with this daily.

What sort of thing would a person in this scenario do to help with this? Are there like, mental exercises or something?