If you are reading a book, do read.
If you are doing some work, do work.
If you are checking emails and social media, do check emails and social media.
If you are chatting with a friend, do chat with a friend.
If you are in a meeting, do be in the meeting.
The point is that you should commit to whatever it is that you are doing at any given moment. Mixing different activities at the same time is a sure way to get nervous, stressed, and eventually achieve nothing.