Why do they spend so much time on worry?

Another question here: My ADHD husband spends an EXHAUSTIVE amount of time worrying about everything. He is now (thankfully) doing many more things around the house that he wouldn't ever do before, but BEFORE he does them, he has to WORRY several days or weeks about it....BEFORE he actually DOES the thing he's supposed to do. This shows up when he has to fix something that's broken, or call someone on the phone, or go to the store or bank.....pretty much anything. There are so many things that would only take 10-15 minutes to fix will take days to weeks to do because he talks about it endlessly and worries that he has to fix it. Is it impossible for them to STOP right then, STOP the worry, and just FIX the darn things? This is why at times, I "took over" doing so many things around the house, because my husband just never DID IT.  I have tons and tons of things to do also, but don't worry myself to death about them ahead of time. What IS THIS? anyone?