How does entertainment glorify God at all? In the modern context, we have many things to keep ourselves entertained and motivated to do work - music, videos, movies, games, magazines etc. 

According to 1 Corinthians 10:31 KJV


  Whether therefore ye eat, or drink, or whatsoever ye do, do all to the glory of God.


It is clear that in whatever we do we will do it for the glory of God. 

However I really wonder how does gaming, watching video and having self-entertainment would do to glorify God.
Entertainment is one way we relax, and the Bible does tell us to rest, in many places, including Exodus 20:8: "Remember the Sabbath."

Entertainment can also be a community-building event, although not as much so in the context of "self-entertainment," that you mentioned.

I would also say that many things are not purely entertaining, but also educational or enlightening.

Having said all of that, I think many of us take entertainment to extremes, to the point that it is no longer glorifying to God. I know I'm guilty of this at times.