Quitting One Job For Another

I quit my job today for five reasons: (1) I wasn't any good at it and probably never would be; (2) It was an on-call, part-time job; (3) Somebody could die if I messed up; (4) I've already been offered another job that seems better suited to my aptitudes and career aspirations, and I'm now just waiting for HR to complete the paperwork so I can get started; and (5) The new job is full-time with regular weekday hours.

Having said this, I feel uncomfortable and even a little ashamed over leaving a job I had only barely begun, especially when my supervisor and co-workers have been so decent and accommodating and have invested so much time and effort and the agency that hired me has invested so much money in my training . And I also wonder if I'm going to be able to do my new job all that much better than I was able to do the old one. That is, will I be merely jumping from one frying pan into another, or, worse still, straight into a blazing fire?

Reservations and questions aside, I sincerely believe that I'm doing what's best for everybody, and I suppose that this is the best I or anyone can do.