a shot of clarity
A moment so sharp it cuts through your brain, telling you you're an idiot for waiting so long to see the obvious.
"I just saw my ex with his new girl, and it hit me like a truck. I'm still stupid."
"I thought I was smart. Then I realized I was just being a fool for waiting so long."
"He came back, and I thought I was lucky. Now I'm just stuck with him again."