I think you just need to love kids.
Uh, yeah, that's all you need - if someone fronts up to an interview and answers the question why do you want to work here with because I've always loved kids, that doesn't earn them alot of merit.
You need to be realistic, you deal with illness and snot and vomit and poo, alot. Parents can be extremely trying - some can be downright rude and sometimes, they make you cry. A group of us were talking about if/how many times, a parent has made us cry in our careers. One out of 8 of us had NOT been made to cry by a parent.
You need to be prepared for children with less than desirable behaviours and who have families with different standards and expectations.
YOu need to be prepared to be unappreciated, alot, and be treated like you are just a babysitter and you don't actually teach them anything.
And you need to be prepared to be paid less for your responsibility than alot of far less responsible jobs, including cleaners or those who look after animals.

That is the realistic view of it.......from the negative.

You need to be prepared to laugh more than ever before.
You need to be prepared to feel loved.
You will feel appreciated by some very special parents.
You will feel rewarded when you know something you've done has made a difference in the lives of others.
You will meet dedicated people who love what they do.

It's not an easy industry to be in to be totally honest. I would also recommend going and volunteering somewhere for a while to get a realistic idea before you make any big decisions.