Still doing great with pain but now nervous because of a dental appointment comming up

I have a dental appointment comming up for my root canal on tuesday and I am so nervous. i have had plenty of fillings but this is different and I do not know wht to expect at all it was not really explained to me at all because when I was suposed to see the dentist who was originally going to do it so he could explain it I found that he left the practice so needless to say I am kind of in the dark with this one. Very nervous which does not help anything at all