Quitting my last job. I had been there for about 3 years and had a great time there.

It was only my boss and I, we were developing software and websites for events so we were quite often out meeting and partying with people, it kinda became a part of the job. We had a fridge always stacked with beer and champagne which was for us and our friends to use. The office was located in the middle of the most exclusive business and club district in the city, so I could use the office as I wanted during evenings to meet up with friends and drinking beer.

But it was expected to work a lot of overtime. I was single and young and really liked what I was doing so I didn't mind. But then I met the love of my life and started to spend more time with her. I couldn't stay and work as often and would rather be with her on weekends.

It became quite hard to live up to my boss's expectations and it always felt like I disappointed him if I didn't (or couldn't) stay for an after work, and when I did, it felt like I disappointed my new girlfriend instead.

Ultimately I felt I had to choose one of them, or I would definitely loose her. It was a no-brainer since I knew I couldn't keep working like that forever, and didn't want to risque a relationship because of work.
It took all of my courage to do it and I felt so bad because I knew my boss (and my friend) would feel like I betrayed him, but I knew it was the right thing to do.

I can still miss it sometimes, but I don't regret it.