The orchard ladder I was using is the taller one in the photo below.
These three-legged orchard ladders are safest for use in working with trees as all three legs make firm contact with the ground even when working on ground that's not level. Securing the ladder to something would be a good thing, but it's rarely done as it's usually just not possible to do since there are branches that interfere with getting the latter into a position that would allow for this. I could have tied a rope around myself and tied it around a branch for safety, but having someone hold the ladder would have probably been the best option.
Most likely, I just pulled myself over by pulling on a branch to lift it, even though I didn't use much force and the branch was just a couple of feet away.
I went back to cut down the rest of the tree three days later (greeted by several of my new neighbors who were delighted to see I was doing as well as I was!) with two workers. I wasn't able to do much other than supervise but I did decide to avoid any lifting of branches from the ladder. I had workers trim off small branches and then put a rope over a crotch of the main trunk about 20' up (required some careful climbing of a worker) and from there we tied onto limbs which we cut off with a chain saw which has an extension pole that goes out 14'. This eliminated most of the need to cut a limb while standing on a ladder and we lowered cut branches with the rope. It was simple and much safer. It's best to avoid having to reach out very far from the ladder, especially with the weight of a chain saw or ladder.
I don't believe in "luck" or "lucky stars". I truly believe I was blessed and God protected me from more serious injuries and I am thanking God several times a day for getting along as well as I am. I hope my lesson helps protect me and others in the future.