Debs wrote:My 12 year old birthday prezzy was a beginners horse riding lesson.
We were taught to mount the horse
[or ponies in our case] on their left hand side; put your left foot in syrup and swing right leg up and over saddle...
So i can only think it all makes good horse sense
You almost always mount a horse from the left side. I was told that this was because of the fact that your sword (and people who rode were the sort that had swords) hangs on the left hip if you are right-handed. Mounting from the left means you don't have to swing the sword over the horse' back.
That also explains why we rode/ride and therefore drive on the left- if attacked from the other side of the road, you want your sword in the hand closest to your attacker. On the continent, they do it differently. I have heard it's because Napoleon just did the opposite to us out of pique, but don't know if that is true.
However, within riding school arenas, you pass left side to left side, not right to right; I think this is a concession to dressage being essentially a mainland Europe thing, I can't think of any other reason.
Some horses you do mount from the other side- but it's very rare, and the average horse might very well get upset if you tried it. They have to learn most operations 'handed'- i.e.,- they don't easily transfer learning from one 'side' to the other, so you have to teach them everything both ways.
In fact, it would be better for them if you used both sides alternately fro mounting, because they can get uneven muscle development from it - at least, in theory.
End result of always using the same side is that the stirrup leathers on the left side tend to get stretched, making them uneven with the right ones (uneven stirrups is bad for balance, as you can imagine- would be like having cranks not at the same height). So the counsel of perfection is to swop the leathers round every time you ride (when you clean the saddle, which you should also do every time you ride). Literally nobody I know these days does either.