It's like a risk flow chart or troubleshooting chart. Do your repairs and maintenance at home not on the road. Use a check list so you dont leave the step out or whatever. From there, have the funds on hand, credit card whatever to cover whatever happens. If you dont have the funds to cover the worst repair imaginable, stay home and sell the rig.
If the water pump dies have one sent to a campground, if the engine blows rent a room and get out the charge card or checkbook. Worry will only get in the way of being cautious and paying attention to what needs attention while driving. We have all gone through this to varying degrees.
My big point is do repairs at home. I may waste some money but I consider it an insurance policy and have been stranded ONE time in 45 years of driving when a Chevy electronic distributor died on a Sunday evening in a rural area. Towed it to dealer. Belts, hoses, water pumps, starters, alternators, axle seals, brakes, bearings are all determinable by inspection or expected miles of life. Some run until stranded some by insurance.