It’s interesting to think about, and don’t want to be a downer but I always had a problem with this saying. Because a positive/good thing happening is obviously not something you would think too much about, because it’s not something you fear happening, it’s like “great, fine”. You also wouldn’t want to get your hopes up and have them come crashing down. However, something negative happening or being a possibility is something you would naturally ruminate on for longer as it’s something you really don’t want to happen. The prospect of a negative always outweighs the potential of a positive mentally imo because one isn’t stress provoking. Evolutionarily this makes sense also, just not to the extent people with SA suffer from it.

We’re primed to avoid threat, that’s how we survive. Thinking ahead/into the future about the possibility of bad things happening allows us to avoid threat. The problem with anxiety disorders is that the perceived threat is thrown out of all proportion, or illicits extreme responses. These can have genuine and rational origins also, but then get generalised in the future which creates issues.

So don’t get me wrong it is important to think about what could go right/well/great/amazingly but it’s understandable why people tend to lean the other way naturally.