The hitchhiker's guide to throw a way a completely won endgame

Yesterday I played for my chess club in the external competition for the first time. It was a tense game with initative swapping sides a couple of times. After a series of exchanges I ended up with a pawn up and a winning endgame. By that time we had been playing for over four hours and I was nervous not to make a mistake. I managed to promote my pawn and my opponent traded his rook for my newly born queen. I should have kept my cool, but I lost it and traded my rook for a pawn, in the belief that I could promote one of my other pawns, which turned out to be a hallucination. After that I was fighting for a draw. I managed to keep the draw, but I thoroughly hated myself after the game for throwing it away. The game is below with full annotations. Enjoy!

Now, after analyzing the game my self hatred is starting to faint. I did play a nice game and although I threw away my win, my team still won 6-2. It was only my first competition game and slipping (albeit badly) after four and a half hours of play is, I guess, human. Just a sign I need to practice more!