I doubt it's anything to be concerned about, but I thought you'd be interested to know of a condition called 'Compulsive Exercise'. It's generally a condition, which a person generally may or may not have control over. It allows them to relieve stress and anxiety through excessive running.
I don't think it's typically an issue, unless this takes over a persons life (ie. prevents them from going to work, or causes strain on their body). I believe it's why Forrest Gump went on his famous run across several states just after his mother had died; it was his way of grieving.
If done at a healthy level though, I'd say you're quite lucky, as many people (including myself) see running as a chore...unfortunately