Wish I knew what to do

This feeling of not being able to make a decision about whether to quite my second job is driving me crazy.
The reason I got the second job was just in case, god forbid something happens to the client from my job. I feel like I should just quite, so that I can really apply myself to doing better in school. I know I cannot do this line of work for much longer, it is getting to be to physically tough. And need to do something else.
I believe the biggest reason why I can't just make the final decision is because I just don't have the faith, that everything will be ok. Paul always told me to just have faith and believe in yourself.
If anything, I was thinking if I do quite this second job, and if need be, could find another second job. This second job, has not given me the hours and I need, to make it worth doing.
I have given myself until tomorrow, to make the final decision. Just don't know what to do.