I've had some serious Peter Principle concerns on multiple occasions.

One of the jobs I applied for - I was pretty sure I could do it, but had some concerns about what might happen if I couldn't pull it off.

My last two job changes have been my direct supervisor coming to me - and in one case just telling me I'd just been promoted and in the other case telling me she wanted to promote me, but I'd have to interview.

So far, so good!

I always worry - as you've expressed - that with each promotion there is no going back. If things don't work out, then I can't go back to my old role. So that means I'll probably have to leave the organization. And I don't like that at all - I've been (or grown to become) comfortable in past roles. So change that could lead to BIG changes are not necessarily something I'm looking for, though they've come to me.