I am having a similar experience, but about to go up to the Mayo Clinic for my third visit in about a month. My fear is more based on things like: did I forget to pack everything I need, will I be alert for an early morning appointment, will I be bored and lonely over the weekend, will I be accepting of all of their recommendations, etc. Unfortunately, I don't have a large support group to provide me reassurance that everything will be ok. I just have to trust that it will and may have to adapt to some physical limitations. I can say that the Mayo clinicians are very thorough, provide results almost immediately, and are courteous and friendly. The facilities are unbelievably clean and I'm sure their diagnostic and treatment is state of the art. The best strategy for me is to plan every detail ahead of time and complete one or two little pre-trip tasks each day, like organizing my meds, withdrawing cash from an ATM, etc. and just letting the future happen without worrying about it too much. I learned that surfing the Internet to read about my problems is a bad idea, because it causes more worries and leads you to believe that you have more ailments than you really do. Good luck and try to focus on the present moment.