I'm scared to ride on his bike

He has been riding for about 30 years and I trust him with my life. I am not a good passenger in a car either because I get anxietal. I feel like I need to be in control. When I drive a car or a boat I'm fine. When I ride the dirt bikes I'm fine, but he thinks that I am not into getting my own street bike because I am scared to ride on the back of his. I'm trying to tell him how much I trust him, I just need to be in control of the vehicle in action. Help!