Regretting accepting a new job

[norma4567]

Anyone ever handed in their notice signed the contract for a new job then just a few weeks before starting, started to think they're making a massive mistake?

What did you do and how did it work out?

Yes, and I even spent the first few weeks in the new job, possibly months, feeling quite miserable and terrified I’d made a huge mistake.
I’ve now been there nearly a decade.