Going back to what's familiar even if not healthy?

I'd love some input from those with ADHD and those who have long-term experience living with someone with ADHD. 

Is it a "common" coping mechanism or reaction to being overwhelmed to give up on something you really, truly want and go back to or stay in a situation that makes you unhappy because it's familiar and easier to handle?  In the bad situation there really isn't a risk of failure because it's already a mess, but in the new situation there is a big risk of failure.

For example:  My ex hates his job.  There are a few things about it he likes, but in general he is pretty unhappy.  So he applies for a new job and is hired.  The day before he is supposed to start, he's overwhelmed, stressed, anxious, and bails on the new job and goes back to the old one even though he's not happy there. 

The known vs. the unknown can be comforting to anyone - ADHD or not, but just curious if this is part of the executive function process?

He does stuff like this all the time.

Thanks in advance for any input or insight!!

I don't know if it's part of

I don't know if it's part of executive function (or dysfunction), but yes, my husband, who has ADHD, would much rather put up with poor conditions that he knows than attempt to try new things.  Witness his total failure to do anything to work on our problematic relationship.  

Stuckiness

Yes. Daniel Amen includes this among his criteria for 'Over-focussed ADHD'.

Intuitively I wonder if it stems from a learning disability.