Worse on holidays?

Title says it all. I wonder if this is a thing at all.

I've been seeing a therapist and got better, and my plan is to continue with therapy.

Before holidays, I reached a point where things were "stable", I could feel myself better, although there's always a "black cloud" feeling telling me something's wrong, except there's nothing specific just this dread feeling or black cloud that something is wrong.

During holidays, a couple days in, I started again with thoughts about not loving my SO, looking at other women and wondering if I'd be happier with someone else, and in general the full specturm of thoughts that come with it.