OMgosh I am the queen of losing weight and then gaining back that much and more. When I moved in with my fiancé/moved away to college I went from 190, where I had always hovered, to a very stubborn 262 in a matter of about a year.
It's awful

but the best thing you can do is start again. For me, I didn't place a lot of expectations on myself, I only lowered my calories to 1700, and I broke my weight loss into four groups of about twenty-five lbs, since I have 100 to lose. I'm only focusing on those 25 at a time. I'm also perfectly content to see oz's lost on the scale, or even stay the same. Okay, not PERFECTLY content but I don't let it depress me, just motivate me to work harder. One day I just kind of opened my eyes and realized its time. And I've only lost eleven lbs but as far as I'm concerned, I don't care if I plateau, I'm never getting back into the 260s. I gain weight sooo fast, so I know I have to stay on myself. I visualize myself as running away from 300lbs instead of running towards it. As long as I'm facing the right way (whether the scale shows a minor gain or not, as long as my mindset is right I'm facing onederland).