> So how can I regain my ability to focus?

Getting diagnosed with ADHD and taking meds did the trick for me.

Not sure how relevant this is, since inability to focus was always an issue for me.

I don't think that the author has ADHD, because they used to be more attentive in the past. In the case of ADHD, it was also the case as a child.

I also got the diagnosis of ADHD (inattentive type) a few months ago, in the interviews they asked whether I also had these symptoms as a child. Not easy to figure out because as a child things like finishing things on time are not so important yet, and my high IQ compensated for a lack of focus. Only in secondary school it became a problem, and my grades dropped.