Fetching details from the dictionary...

frustrated (over a failure, humiliation or injustice); annoyed; chagrined; (bitterly) disappointed; bitter; vexed; frustrating; annoying; regrettable
あと一点で合格だったのが口惜しい。
It's frustrating that I was just one point away from passing.
あと一点で合格だったので口惜しかった。
I was one point short of passing, so it was frustrating.
全力を出し切ったから口惜しくない。
I gave it my all, so I'm not frustrated.