in my experiences of being a distance runner for 20 years (PB 15 for 5k and 29 for 10k) I would say that it made me harder and selfish as i was totally committed to running and the local club from age of 13. Had no time for anything or anyone as my coaches have made sure i was pushed hard (70-85 miles per week)during my peak (aged 23).
my communication skills have suffered due to hours of training alone and in team. Limited conversation except athletics made it hard to form relationships.
But it has made me focused, reliable and hard working.
Only job i have had is in sports retailing as they understood demands of running and made allowances for time off for races etc. Now area manager for medium sized sports company. Enjoy coaching senior mens xc team so have never got away from running- but have had some great achievements despite the hard work mentally and physically over my athletics career- which has always come first!
Dont let the loneliness of the long distance runner put you off!Use it to your advantage man!