advice please

i am about to go into school to become a cna, and then am planning to become an rn. i have a questions for all of you though. how do you/ did you know you made the right career move? i think i'm kinda getting cold feet now that i am so close to actually going to school. i think i will be able to do the job, but i am a little scared thinking that maybe this isn't my calling. everyone has said for years i should go into nursing, and i could never see it. however, i really need to make a career choice, i'm just nervous about it.
so, now that i'm done rambling, how did you all know this was the field for you?