Apparently, post-traumatic stress symptoms are common in people who've experienced traumatic accidents, such as traffic accidents, involving broken bones, or head injuries, or hospitalization. It also makes sense that this happens after a serious riding accident. One common symptom is refusal or reluctance to engage in the activity that led to the accident, and envisioning possible negative outcomes from engaging in the activity. Some of you in your comments have noted my dread/lack of enjoyment from riding my horses, and that's certainly true.
This understanding comes as a relief to me - I'm a bit slow on the uptake, apparently. I'm not old, or incompetent, and my horses, while they may be challenging at time, are just fine. It's just that I'm still processing, mentally, emotionally and physically, the effects of the accident. My reluctance/dread/lack of pleasure in riding and working with the horses are perfectly natural effects of the accident. There are some things I can do to help work this through, including consciously directing thought patterns into more positive stories ("reframing") as my horses and I come through this together.
This validates for me my plan and goals for 2012. While my horses are on "winter vacation" (you should see our arena - it would have qualified last week for ice hocky events), I'm planning to take some lessons on easier (more thoroughly trained) horses to get the habit of riding back and solidify my abilities to ride "in" rather than on, the horse. I'll also be working with an experienced trainer who's a student of Mark Rashid, probably starting in March, as I bring my three horses back into work, so she can oversee and advise with our getting back into business. I'll be working on my core strength and stamina, as well as my balance, to make sure I'm fit to do what I want to, which is work with and ride my three wonderful, full of personality horses - Dawn, Pie and Drifter deserve nothing less.
P.S. - read the comments - there's more interesting stuff in there . . .
(A very big thank you for all the supportive, insightful and challenging comments - I very much appreciated them all and they were a great help to me in thinking these things through. And read this post of Mugwump's - that's where I want to get to with my work with my horses.)