I wanted to be a pilot from an early age (4) when I first went on an aircraft. Simple answer - I loved it.
It then developed throughout my life, the more I learnt about the job, the more it appealled. How many offices have a view like that (ok a grotty winters day there's not much of a view, but to climb out of it does it for me) There are no telephones! There's always a chance of travelling the world and seeing new places, meeting new people. I could think of and have done worse jobs that have been paid far less too!!!
But I guess the bottom line for me is that I enjoy flying, why not do it for a living.
All the best, Le-Slat.