I'd echo what WWW has said about commitment and determination, and add that you need to be well aware of the very real possibility of dying in your military aeroplane. And most fatal accidents are on training sorties, not in war.
That said, there is no finer flying anywhere. It's a bit like the comparison between motorbikes and cars. Both will get you where you want to go, but one is a hell of a lot more fun. You can always buy a car later! The girlfriend never likes this plan...
It's no good, 10 years down the road, wishing you'd had a go when you were young. You can't do airlines and then go military, you can only do it the other way round.
I did it for 22 years and now fly big aeroplanes for a big company. My memories are terrific, in spite of some serious butt-clenching at times! I'm not sure that 27 years (now) of civilian flying would have given me the same...