I think it is reasonable to be nervous, but I don’t think moderate nervousness would cause constant crying. You are embarking on a great adventure, and everything will work out. It usually does, right? Although I am one to focus on the big picture in most situations and encourage others to do so too, in this case I think that you have to focus on what is right in front of you. Thinking about all of the problems you need to solve could become overwhelming and that may be why you are crying. Enjoy the moment that you have right now. Hopefully it turns out wonderful and I wish you all the luck in the world.