I would talk to a professional about this. You have to nip it in the bud. The go for a short ride on the road and then go home again. Whenever you work a horse hard like that, it is best to either ride them at the walk, or hand walk them to cool them out. I'm sure your horse will be ok, but you really shouldn't do that in the future, especially in the rain, because they can become sick.
Horses are unpredictable.
If you are not experienced, handle horses under the supervision of a qualified instructor. This forum is not intended to be an instructional guide, and any one who uses it for this purpose, does so at their own risk.