That is perfectly fine, I respectfully disagree with you too lol. You say tool, I say crutch, tomato/tomato eh?
Not quite tomato/tmato, as it isn't just a differencwe in terminology, but a difference in the opinion of the equipment. But close enough :]
However, I ahve also already stated that a martingale would be useless in this situation, OP has accepted that and moved on, so all is good :]
OP - My first pony actually did the same thing; Rearing when I was mounting. She started it when I took her to our first PC camp. She would get horribly excited in the mornings with 300 odd riders and horses saddling up and moving out. I was about 11, but could handle her pretty well (She was a pesky little welsh mare) and I was absolutely horrified when they insisted on leading me around like a 5yo because of it. It took a few days to convince them I was fine and could handle her myself, and as she got tired throughout the week, it stopped.
Obviously different to your situation!
We will be able to give more advice once we have some more info - As JDI asked, what tack you are using, how you go about mounting, etc.