What I learned working off my seven Thanksgiving plates running/hiking 46-54 (depending on if you ask the Internet or my GPS) miles, and climbing ~10k ft through the Grand Canyon...
There was a sign on the first descent "Going down is optional, coming up is mandatory." I thought about this not so much as I trotting down the gentle slopes, but very much as I stumbled up the final 4.5 miles, heaving and trying to keep from crying and my heart to stop beating like a hyperactive college kid on adderall. I said no less than 5 times, "I can't do it, I'm just go to stop." Then I'd realize that wasn't a really an option. Well I could stop but that most likely meant I'd a) face hypothermia, b) a bobcat eating my face, c) or an embarrassing and expensive rescue from a park ranger only a few miles from the rim. Morale of the story is that it's easy to get into something - a bad relationship, addiction, unhealthy lifestyles, financial issues, legal problems, a canyon - but is a lot more work to get out of it. Still coming up is mandatory, one foot in front of the other and if telling yourself you CAN do it doesn't work, remind yourself that you HAVE to do it.
Microspikes are the s. h. i. t. Especially for clumsy, graceless folks.
I've never been worried about being alone in most areas of life....except these types of adventures. After the first seven miles or so with Linda, and a few miles with my old CG's niece (small world) I completed the majority of the distance alone. I knew this going into it and almost cancelled the whole trip, but I figured it was time to learn how to be alone - to learn how to pull myself out of dark places, to be the only one responsible for me. I wasn't entertained by anyone or (gasp) the center of anyone else's entertainment. I didn't like it. I would have given my next paycheck to have just one of my friends or family with me, to share my misery. But being alone has its utility - and I learned a lot about myself in the 15 hours I spent wandering through the wilderness. You cannot and should not go through life alone, but you absolutely need to know how to be wholly self-reliant and comfortable with just yourself.
Finally, probably my favorite realization, you can accomplish anything as long as you're willing to sacrifice time and comfort.