I am no psychologist, but the flow state seems to be the term. The situation in which one’s attention span is the most stable and can go on for a long period of time.

I for one seem to have significantly achieved this only once in last year, that is during the writing and research of my thesis from May to June 2016. A feat that I surely miss. I can’t seem to enter the flow as dedicated as that, after three months into this year.