Definitely NOT the end of the world! I'm not sure what your current weight is, but you possibly just ate your "maintenance" caloires...meaning, no harm, no foul! Get back on plan and you won't even notice it. No way you gained 12 lbs in one day

I know that sounds stupidly obvious, but sometimes we just need to hear it! I get it though...feeling like one bad day "un-does" all your hard work. It doesn't. Just don't ride the "slippery slope" and you'll be fine! Chin up