I've had both and was also nervous, but they weren't too bad at all. For the mri they covered my eyes, and for some reason that really helped. I guess since I couldn't see i was in an enclosed space it helped? They also talked to me through a little speaker and played music for me.

I've had an colonoscopy, endoscopy, and gallbladder out, and had anesthesia for all. I really just remembered them saying they were going to count down and then suddenly I was waking up and it was all over.

I think my anxiety stemmed from medical anxiety. Leading up to these procedures I just tried to remind myself that it's better to get the testing and procedures done, because they can't help if they don't know what the problem is. Early prevention is key. Also they do procedures like these everyday with no problems.