You can get over your phobia by gradually increasing your exposure to that which you fear. Go out into the open part of the camper for a awhile, then look into the overcab area and assure yourself that it is safe, it is the very same place that you are now sitting in. In your minds eye, picture yourself up there, all calm, relaxed and safe. Train your mind to KNOW it is safe up there. Do this daily until you can picture yourself up there and remain totally calm, at least for 30 days. Then go up there for very short periods. Be mentally prepared. If you start to feel scared, leave and regain your composure, use your logic to show yourself that there is nothing to fear. Then go back up there, and gradually increase your exposure untill it is no problem. Use the same proceedure to tackle any other place you fear. Good luck.
2018 Eagle Cap 1163 triple slide, 400W solar, MPPT, on a 93 Dodge D350 Cummins, DTT 89 torque converter, big turbo, 3 extra main leafs, Rancho 9000s rear, Monroe gas magnums front, upper overloads removed, home made stableloads, bags.