So it's not just your ability to stand up to the physical demands, it's also a question of several other required elements of running a successful business--and truth be told, a little luck besides. People often possess the stuff to succeed, but are set back by circumstances beyond their control (fate, bad luck--call it what you like).
Besides the physical side of tree work, you need to be able to talk to customers and gain their trust. You need to figure which investments in equipment will pay off, and which will saddle you with too much debt, or will drag you down with repair costs. (The more equipment, the more maintenance, and if you let that go you'll wish you hadn't.) You need to hire--and then keep--good help. You need to know how to balance family and business--believe me, this will come up. You need to know how to price your work, a fine balance between pricing yourself out of work or selling yourself too cheap. There are probably a few other things, but this gives you an idea.
Probably the best advice I've ever heard about starting ANY business, is to have enough cash on hand to see you through the first year when you can't expect income to outpace expenses.
You might be the perfect candidate for this work, or you might try it and fall flat. No one can tell you which. There's a certain fulfillment to running your own show, but everyone who does it has had moments of "How did I ever think this was better than drawing a steady paycheck?"