Unsolved problems drive humans crazy.
It's difficult for us to understand that some things happen to us for no reason at all. We're desperate to identify cause and effect. If we can't find one, we'll make one up.
We try to trace our emotions back to a root cause. What (or who) is causing us to feel this way? Given that this is a subconscious process—we're rarely putting deep thought into fleeting feelings—the cause we assign can be automatically attributed to suspects that are top of mind.
This results in misattribution... A LOT of misattribution. Known problems undeservingly collect blame for unknown problems.
Here's the scenario:
You've been struggling to stomach a recent change in your life. This is a touchy subject you haven't yet fully come to terms with yet, but you've made some progress. You're beginning to accept the change. (Good job!)
Then, on an otherwise peaceful Sunday morning, you realize you're in a bad mood. Naturally, your mind starts hunting for a plausible culprit to blame for your seemingly random bad mood. It doesn't take long before a familiar, top of mind problem is deemed guilty. Your mind is an impatient detective who sometimes incriminates the first suspects its finds.
Your Sunday blues could have been a result of anything—or nothing at all. Maybe what you perceived as a bad mood was only a brief period of boredom or hunger. Doesn't matter. Your mind quickly decides the story adds up: an existing problem bothered you before, therefore it is plausibly responsible for your Sunday blues.
Your existing problem, the wound that had begun to heal, gets re-opened. All for the sake of (incorrectly) assigning a cause to your feelings. And now you're going to need even more time to heal back to normal.
I don't have a solution for this.
I suspect that by noticing our emotions, without associating with them (I'm noticing that... instead of I'm feeling that...), we might be able to reduce how often we search for cause and effect.
Understand that currentlifeproblem probably carries more blame in your head than it deserves because your known problems are collecting blame for your unknown problems.