I think a career in aviation makes you extremely focused and yes, selfish. You have to be single minded and if there's someone in your life who doesn't support you 100% then the relationship will suffer.
I've had experience of this firsthand. When I started learning to fly it caused a great deal of tension as my focus turned to aviation and has never left it since! My partner took it all very personally and he couldn't understand why I'd changed overnight.
If I am honest I would have to say that flying has changed me - in some ways for the worse but in other ways for the better. Now I have the attitude that this is who I am and if someone can't deal with it, too bad. But then again, someone could argue that proves that I am a self absorbed and utterly selfish person!
