I've been working on a research problem for several weeks. The details aren't important, but basically I've been trying all kinds of advanced math and physics tricks to solve a particular system. Then this morning I realized that the solution was literally as simple as rotating my picture of the system by 90 degrees, and it works with no additional tricks.
Enter, a strange combination of excitement/relief that I finally have the answer and frustration/embarrassment that I didn't think of it sooner.
When I went to describe it to someone, I realized how odd it is that I have no word/phrase for that feeling, considering how universal it seems to be. Everyone has had those moments where you realize that you've just been completely blind to something that seems like it should have been obvious.
Sample sentence: "I was looking for my sunglasses for ten minutes; when I realized they were on my head, I felt so <word>!"
I searched on thesaurus.com for synonyms of:
In particular, I didn't find anything that bridges the positives and the negatives of this particular emotion. If such a word or phrase exists, I'd love to know what it is!