I can relate. I have not had any specific injury that made me extra fearful, but I am out of shape and never too keen to ride through any serious bucks or rears.
That is why I have to approach things from a place where I hopefully don't get into that place where I push real hard (like a really smart, hard snap of the whip, or an over-and-under with the rein ends, etc) and the horse meets or exceeds that with his push back, (buck or rear), which I am not sure I can deal with. This depends on the horse. Most horses will not be that bad. but, if I'm not sure, I don't go there for fear of losing the battle.
You don't want to put yourself in a place where you cannot meet that pushback, because that only teaches the horse to rise to that level quickly every time he doesn't want to do what you ask , in order to get away with things because he knows you cant match him.
So, that's why training approaches that sort of 'bend' the hrose, rather than meet them head on are what I have to do. If they balk, I break lose the feet with bends and lateral stepping. If they go to fast, use circles to slow.
If they are goint toward the gate, get their mind on something else before it is really FIXED on the gate. That way, you don't 'beat' them out of that hardened fixation, but rather sort of 'bend' them into another activity, before they even really were thinking much about the gate.