Same thing happened to me in the early 90s flying from SFO-HKG. I was in the upper deck, sitting next to a UAL HKG maint. mgr when we hit severe clear air turb. He just smiled--as the 744 wings were bowing up and down--and said, "you know, those engines are just held on by 4 bolts." He was completely calm, which helped. Though I have no fear of flying that was a rather uncomfortable few minutes.

After the turbulence subsided it was clear for the balance of the flight. As I recall I may have had a few extra adult beverages to settle my nerves.