Some kind of 'crisis' is inevitable (probably
). It really amounts to a series of 'What if this instead of that?' and taking stock of your life, what you have vs. what you wanted, and so on. I've done a few rounds with my disquiet (and disquieting) thoughts and seem to have put them away, only for them to rise again. They'll do that, you see, because they're ghosts.
There's no trick to get around it. Even if you live a life with no regrets (or no big ones, anyway), you'll still hit a point where you ask yourself the question 'What if this instead of that? What if I'd done/chosen Y instead of Z?'
Personally, when I was younger I did the things that seemed right at the time. Other things I couldn't do anything about, as people did what felt right for them. Of course it meant that things didn't always go the way I wanted them to or work out the way I thought they would (or ought to), but...c'est la vie. Knowing that hasn't stopped me mulling over things and wishing they were different or that I could have a do-over, though, and some things are harder to make your peace with than others. (There's one thing I can never make my peace with, so I have to settle for making my peace with that fact.)
The main thing to bear in mind, really, is that you can't have everything you (think you) want. Again, that's life. If there is a trick, it's to get most of what you really want and come to terms with the rest.
But as
Tery said, you have some warning. You've seen what can happen. You can now prepare yourself by asking 'What's the worst thing that could happen?' and then refusing to let it when the time comes. (That's not a bad thing to do in pretty much any situation, tbh.)
But...on topic: What terrifies me?
Not that much. Bugs getting in my ears and starting to burrow and/or lay eggs, is one. I dislike spiders intensely. I hate snakes. (So that's me never going to Australia, then...
)
Alzheimer's, I guess. And being in an accident that leaves me mentally impaired. I'd honestly rather die, because I'd no longer be 'me' (losing limbs, I'm fine with; I could also probably handle becoming paraplegic but not quadriplegic).