Mounts and broken defiance?

I was trying to mount my raptor and since my computer was so slow it wasn't working right away so I clicked it again to try and cancel it or something? I ran a little further but then for a split second I was mounted and then unmounted and where all my attacks were was just the tail spin and the mounting option . There was also a red shield with a grey bar above the right side of my attacks and when I hovered my mouse over it it said 'Forced Dismount, Forcibly dismounted, occurs when defiance is broken' and I can't find anything about this anywhere. What did I do? (I fixed it by logging out and logging back in)