I have no hard data to prove that my rational thinking is improving, so maybe it isn’t. But here are the things I am trying recently:
Reduce the social media: I almost stopped reading Reddit, and there are days when I don’t use Facebook. Now my major distraction is Hacker News, but I try to reduce that, too.
I downloaded and read a few textbooks, mostly on math. The idea is that if I am curious about something, e.g. set theory, it is more efficient to get the fundamentals right first, and only then proceed to more controversial parts. (Here, the rational thing is not the information I get from the textbook per se, but rather the habit to look at the textbook first.)
I tried to meditate again… but this was only a week or two ago, so no results to report yet. (The expected benefit is to be able to focus better and reduce distracting thoughts.)