Use your fear and negative mindset to your advantage.
Instead of saying....what if I die of this surgery? (you won't)....say to yourself....Statistically, if I continue to be obese I am at greater risk for heart disease, stroke and cancer.
Be more afraid of the effects of remaining obese.
It's statistically much smarter to be afraid of heart disease, stroke and cancer....than a surgery with less morbidity than gallstone surgery.
Also...they tested the heck out of you. EKG, bloodwork, chest films, GI study.... Having a life threatening surprise under these circumstances is almost unheard of.