For the personal satisfaction of knowing that you made a diffrence in some one's life that you gave them an unforgetable memory and when all is said and done they will remember it for years. And you obtain the personal satisfaction of knowing that you helped some one. And the loud sirens/adrenaline rush and flashy lights are all just an add on.
Hmm, lets see, a tipslip at the end of the month, long hours, nights shifts, always in the dwang...
Just kidding, i would say they you should tell them what they want to hear, but in such a way that don't realise it. But speaking your hart, cannot be wrong either.