I was there for a decade. I essentially placed myself in a prison of conditions I refused to break and/or meet. However, I was able to finish two graduate degrees with a 3.6 and 3.85 GPA, respectively. But I suspect that's because there was an immediate reward for my effort. It was life that depressed me... because no matter how hard I seemed to work, the reward was based on the ability to fake excitement, something I just wouldn't or couldn't do.
School had an immediate reward for hard work. And I also put on 300lbs... because that's an easy reward too. Since 2010 I've slowly worked my way out of the depression and lost the weight. Though, in the time I was in that depressive state I lost everything I'd worked to achieve.
My biggest issue, in trying to climb out, was the finish line seeming impossible to reach. I don't think people who have never been in this situation can even imagine how desperate that feels, and how much it motivates you to keep doing more and more self-destructive things.
After 7 years of this madness, I decided to stop trying to reach the finish line and instead bring the finish line to me. So I set small LONG TERM goals. I stopped setting short-term goals because the depression tired me out, emotionally, so I needed small, easy goals, with a long lifespan. Like... stop drinking soda and replace it with water, or juice, or something. Do that for a year. Change nothing else. I know that sounds like very little, but to get over one poison gave me a feeling of achievement that was more powerful than losing 20lbs in a month... and then putting on 40 6 months later. I didn't lose much weight doing this but it showed me I could.
Next I set a long term goal of losing 50lbs.... over 12 months. I calculated how many calories I would need to eat and discovered I could eat A LOT, but I just needed to cut out little things I knew I could do without. And that first year I lost 50+ lbs. This was a major victory but I still couldn't see the finish line.
I tried to motivate myself to exercise... to write... to make music (I was once a musician but hadn't touched my guitar in years) but I'd start and the depression would kick in and all the doubt would eat me up and I'd almost spiral back to the place that had driven me to over 550lbs. So I put it off and set a realistic goal... when I'd hit 400lbs I'd try again. The current diet was working and I wouldn't mess with that.
A year later I broke 399 and I STILL COULDN'T SEE THE FINISH LINE. But I knew I could get there... so I set other long-term goals which included exercising 5 minutes every day. Just 5. I'd build from there. I knew I could do 5. It took SIX MONTHS of doing 5 minutes a day before I moved it up to 10. Another six months before I was doing 15 a day. By that point I was near 300 lbs.
I could finally see the finish line. It was a year away... and you'd think I would be happy about it but I wasn't. That dread that had gotten me to that point still existed. To this day I still feel like a wave of fear of going to crush me... but I make it through by sticking to what got me here.
Eat right. Exercise. Reward only on pre-set days and only for preset number of meals. Write. Play music. Do something proactive for others. SLEEP (this is something I didn't do much of during my deepest depression).
What I tell everyone who asks me how I did it is this: don't put so much pressure on yourself to reach the finish line. Bring the finish line to you... with the knowledge that you'll have 100 more down the line.