Go you for making it happen. I hear you when you say it sucks.
Your brain was awash in all those love chemicals, it's a high, and you cut it off because you did what needed to be done. The rollercoaster ride came to a sudden stop. I'd be emotional and crying, too.
I hope you feel better in a week or so and take heart in being the good guy. Six months from, you'll look back in pride instead of regret. But that doesn't make it suck any less now.