I took the liberty to look the major symbols of this dream up in a dream book, however, I'll tell you that when I first read your post, I felt that it was showing your strength and determination to get away from your ex. It showed to me that you would continue on your path away from him, though he may come after you for awhile--he'll never be able to interfere with you.
The fact that you were thrown from the horse and lost the saddle, but thrown into a fenced in area, where the ex could not get to you--to me was saying that you may hit a few bumps in the road along this path, but not to worry, as you will be safe from your ex, and he won't ever be able to reach you directly.
Now, those above were my immediate thoughts on the dream, but this is what the dream dictionary and me googling the symbolism of horse had to say.
HORSE:
To see a horse in your dream, represents a strong, physical energy. You need to tame the wild forces. The dream may imply that you have been horsing around. Or perhaps you need to be less arrogant and "get off your high horse".
To dream that you are riding a horse, denotes that you will achieve success through underhanded means. You lack integrity. If you are riding a horse that is out of control, signifies that you are being carried away by your passions.
SADDLE
To see a saddle in your dream, suggests that you need to freely pursue your goals. Do not let anyone hold you back from achieving goals.
To dream that you are sitting on a saddle, signifies that you will rise to a position of prominence and power. You may be exercising control over someone or a situation.
FENCE
To see a fence in your dream, signifies an obstacle or barrier that may be standing on your path. You may feel confined and restricted in expressing yourself. Are you feeling fenced in? Alternatively, it may symbolize a need for privacy. You may want to shut off the rest of the world.
To see animals jumping over a fence into an enclosure, foretells that you will receive assistance from an unexpected source. To see them jumping out, signifies loss in trade.
SYMBOLISM OF HORSE
A summary of symbol meanings for the horse is as follows: power
grace
beauty
nobility
strength
freedom
As a Celtic symbol,the Horse was associated with war. With war, comes attributes of victory, conquer, longevity as well as procurement of territory and other spoils that come with triumph in battle.
SYMBOLISM FOR SADDLE
saddle
A Saddle signifies preparedness for active service.
The color of the horse is also significant, so ask your mother if she recalls what the color of the horse was?
I hope this helps.