When is it not appropriate to ride, weather wise? I am thinking about rain, the cold, windy conditions-when do you not ride your horse?

I'd also think about a rain, snow or just "bad weather". If I wouldn't like walking in that weather I don't think I'd like to ride a horse. Plus I'd be scared the horse might get a cold or something from this ride ...

If a horse is not injured or sick or bad weather, are there any other times you shouldn't ride?

I wouldn't want to ride my horse in conditions that I myself wouldn't walk in. I am not riding my horse for a few months because she is pregnant. As for weather, I never ride her if there is a thunderstorm (they scare her), when it's raining buckets and I definitely never ride her when it is cold.

When the horse is pregnant, and of course it is a good thing that you don't ride her, but how much exercise does she get? How often and how much does she need exercising?

I would agree, if I won't/can't walk safely then a horse should not get ridden. Its bad enough walking if its slippery, let alone carrying something which changes your balance. Most overly pregnant mares are not ridden, but rather hand walked or turned out for exercise as they still need to be exercised, just in a safer manner.

When one is pregnant, what is a good time to stop riding and lessen exertion for the animal? I have been pregnant twice, and I slowed down about 4 months into it all, but I'm sure its a little different for horses. :D

The vet told me that I shouldn't ride a horse throughout their pregnancies but to give them exercise by leading them around the pasture. He also recommended not riding them in weather conditions that would cause them to panic and throw me off.

When you are in a bad mood, don't ride horses. There are two probable things that could happen if you ride in a bad mood. Either you hurt the horse or the horse could hurt you because the horse could sense your mood and adjust to so the horse might also acquire a bad mood.

Weather is a good key to look out for but I have noticed the few times I have rode after being sick even a small illness I never feel quite right. I would suggest giving yourself a couple extra days, I have been known to ride when its nasty weather out, just on the chilly sick but always end up being sick afterwords.