I've never enjoyed the term "positive thinking".
Too many people have used that term, in an almost cult like way, to pretend that all you need is to act like everything is great and you'll get rich, successful etc. I always think of Tony Robbins
So I prefer the term 'helpful thinking', and sometimes try to see if thoughts are helpful or not.
The mind likes to wander, and it should. When thoughts become unhelpful, it's worth considering if more helpful thoughts can be found..
For example, a thought might be that the planet is heating up and weather is getting more extreme. That thought might be helpful, or it might evoke anxiety. If it evokes anxiety, it could become a thought about
how people will become more aware of the environment, and turn to cleaner ways of living or something like that.