here is one little tip that i can tell you about that i found threw personal experience. Once i got a gf i spent many hours on the telephone with her. I found i was not getting to sleep early enough and was very tired for workouts and races. Relationships definitely change your lifestyle. This wasnt because my girl friend made me stay up it just sort of happened. If you are very determined to put running first and everything else second, then there should be no problem (with your running atleast). However i am still going out with this girl and now (its been over a year) i sleep whenever i damn please. I guess the staying up late was just a thing and dedicating tons of time to her was something that faded in time.