For me, when I was my lowest weight, I was at university (which I love more than anything else, because I love learning), with a significant other (for the first time in my life), and again, at my lowest weight which felt amazing because I'd never been that size for 7 years. I was eating 350 calories a day and exercising every day for 2 hours so I was starving, but I was constantly distracted by school where I never brought food, talking with my SO, which distracted me from eating, or exercising so I couldn't eat. It felt like I was "in control", and I was losing weight, so I was "happy". I'd only been sick for about 6 months to a year at the time, so my eating disorder hadn't progressed to I was so sick that I couldn't see anything positive from it.
Now I associate it with being sick and frantic, but I can't give it up.