Firefighting is more than just spraying water on a fire. Firefighting is searching a building that is on fire for someone that may be trapped. It is a very physical and demanding job that goes from 0 to 100 in an instant. Depending on where you live, there could be days without an incident. Therefore the danger is greater because you must continue to hone you skills on your own and be self motivated. Firefighting also involves medical emergencies.
With turnouts and SCBA you looking at an extra 40 pounds easily. Turnouts are hot even in an air conditioned room. Imagine being in a building that is on fire.
Again the danger is underestimated by the general public. When you go into a smoke filled room at night and cant see anything and you loose contact with the wall you came in on and you get away from your hose you could die.
As long as you are mentally prepared, disciplined and in good physical condition you will be fine.