When you have to juggle writing with a day job it can be hard to find time to focus.  I've often seen it recommended that you should turn down invitations and become a virtual recluse if that's the only way you can make time to write.  
Of course, you need to be disciplined, but if you shut yourself off from the world you lose touch with it.  Not only do you risk forgetting how to make conversation (and therefore how to write dialogue), but you can all too easily lose perspective.  If nothing else, you need your friends, to cry on their shoulders when you're rejected, and to celebrate with you when you achieve success.
I've found that obsession is rarely good, and some things are more important than writing.  Maybe that makes me less of an artist, but hopefully, a better friend.