Write down everything you do and honor it as an accomplishment.
Getting out of bed. Reading an article about your craft. Brushing your teeth. Showering. Dressing. Reading somebody else's PR. Commenting on somebody else's PR.
Every. Single. Thing.
Attending a meeting. Having a hallway conversation. Answering an email or ten.
Not taking your own life. Surviving. Not doing other self-destructive things.
Chances are, if you are able to get out of bed (not always a given) you probably did a lot of "little" things. Those are achievements. And in your depression those things may have taken more effort than running a 5-minute mile.
Sure, the goal is to eventually accomplish more. That's fine. But honor the things you're doing.
And hey... good luck.
I believe everyone has times of marginal productivity in their lives, maybe some more than others. But if you can average out ahead of the curve, what does it matter? Showing the fact that you've had a slow week but finished the month on a high note seems like a great capability.
And if an employer doesn't recognize this and can't measure your net output, then hopefully another employer can.
I've had a lot of stress at work. Here's how I dealt with it:
I was once working for a boss who was really infuriating to deal with. To prevent myself from exploding at him, I would take a break, step outside in the beautiful sunlight, put in my earbuds, turn on some good music, and run. I channeled my frustration into exercise. I'd especially make a habit of doing this just before I ate lunch, which would stimulate muscle growth and make me happier and healthier. Somehow that stressful job got me into great shape.
I was once working at a place where all the policies were dysfunctional and things were constantly on fire. I dealt with this by pulling out my phone and using the Headspace app to think about nothing for a moment and calm myself down. When I got back to the work, I'd put on some "focus" music (music for programming, studying, etc) that would help me maintain my calm mood when implementing the fixes. I learned to distance myself from the problem and get people to talk to each other to work it out instead of having proxy arguments on other peoples' behalf.
I've had some pretty bad sleep problems as well. I got into the habit of playing videogames late at night, which really destroyed my sleep. It's really hard to sleep right after staring at bright screens and experiencing intense action. Now I have F.Lux or Night Shift enabled on all my machines and I avoid playing console games at night without wearing yellow safety glasses. Also, I've started adding concentrated lake water to my drinking water since a magnesium deficiency can make it difficult to sleep.
For depression, perhaps learn about Taoism?
If you really can't cope with the job, quit. It'll be even more stressful to try to find a new job while you're already working one. You can search for a new job using TripleByte, which saves a lot of time since you just have to do one coding test instead of 20.
Hope this helps. Good luck.
I completely agree with taftster in a sibling comment.
But burnout is an awful feeling. You aren't able to work. For me, I would stare at the screen for hours on end without being able to get started.
I found that 2 things helped me the most. First the pomodoro system. You are probably familiar with it, but just in case: you have a 25 minute session, where you devote yourself to nothing but concentrating on work. For me, it's unbelievably important to get my first pomodoro in as early in the day as possible. I also found that it is just as important that this pomodoro is coding: not reading mail. Not doing a status update. Not having a standup meeting. Not investigating some bug. I've got to write code as soon as I can in the day. That flips a switch for me. Very important, especially if you are burned out: show up for work significantly before your fist meeting of the day -- the meeting will suck the life out of you and you need some life to suck.
The next thing, strangely, is a TODO/log of what I'm doing. Being burned out means that everything is a barrier. Usually the barrier is too high, so you are stuck staring at it with no idea how to get over it (because normally you would just step over it).
When I first start a pomodoro, I write a TODO of what I'm going to do for the next 25 minutes. I find it's best to spend as little time as possible doing it. Just write down the first thing that comes to your mind about what you need to do. Write 3-4 items at least. Then start tackling the first one. Inevitably, you will find that your TODO was not good -- because you didn't spend time thinking about it. As soon as you realise what you need to do, update your TODO and then do it.
It's tempting to write the code and then write down what you did. I find that it works best to do it the other way around even though it breaks the flow. When you are burned out, flow is quite hard to maintain and any distraction is going to grab you hard. By focussing on making sure your TODOs are correct, it means that you can easily jump back in.
The biggest thing to realise is that you will often be punted out of the zone and will be staring at your screen. What you need to do is to say to yourself, "Just one more" -- which means, making an easy TODO for yourself and writing the code to fullfil it. Then "Just one more". Eventually you will get distracted. When you finish being distracted, turn on the pomodoro timer and say, "Just one more".
At first you may find it hard to do more than 4 pomodoros in a whole day. Don't worry about it. Just try to do as many as you can. Then the next day try to do more than the previous day. I have found that I can claw my way out of burnout pretty quickly like this. It doesn't take long before I'm enjoying my work again. After that, the productivity starts coming back and things start to feel easy again.
Hope this helps.