I have read that one must only work on 3 major tasks within a day to be productive. Is there any truth to this or even anecdotal evidence? Or maybe there's some other magic number? I do feel it depends on the individual but in general, what is the ballpark?
I have tried it and I feel it helps me keep my sanity when I have so many things to do. But I do have to push back other tasks to several days (even if I feel I can fit them in a shorter time if I just "put more effort").