I feel nervous and badly about it even if it's someone I have made a good impression with and has expressed that they would be happy to write one.

I just find the whole application process to be confusing and stressful and I often need a lot of help filling out applications because I can't tell what I'm supposed to write or not and then I have to ask references EVERY time, at least for some of them. I can't hardly bring myself to ask them to be a reference once, let alone every time.