The thing that comes to mind for me is finally passing medical school.
I'd done ok throughout my time at uni, not spectacularly but good enough to ensure I never had to be too worried when it came to exam results day.
Then came finals. And I **** it up royally.
Cue days of utter despair and jealous fury as I watched my friends celebrate and prepare to jet off here, there, and everywhere on their medical elective rotations.
Cue excuse after excuse when people invited me out to celebrate, and all that awkward 'chin up' bullshit people do when they're trying to make you feel better.
Cue weeks of the hardest studying I've ever done, all the while trying to repress the thoughts of failing again and throwing away the last decade of my life (previous degree plus hospital work experience).
And then the day of resit results came, and I sat there drinking myself to distraction and playing Max Payne 3 until the results were out.
I've never known relief and joy like it