What worked for me was a combination of things:

Physical exercise. 2 years ago I got scared because my bad back condition got worse. When I went to a therapy, I noticed exercises (with swiss ball) seemed to help me the most. I'm supposed to do them daily (they take 40 minutes each time), but by trial and error I figured out 4 is the sweet spot. Anything more and I get overtraining.

To answer the article: how do you even start ? You simply start small. Performing the required number of repetitions is not important at all, and sometimes even counterproductive because you're tempted to use bad form to achieve your goal. Keeping your schedule is SUPER important. Exercise yields best results when it's regular, and this in turn tadaa!! builds character. No, really. I would argue working out even a little is more about willpower than anything else.
Then I started adding other exercises to feed my vanity and make up for my insecurities. I always looked like a nerd. I added push-ups. Then squats (both 3 times per week). Quick tip: wall facing squats make it impossible to cheat. If you can't do them, do some stretching exercises and look up some progression exercices.
I don't recommend running to beginners because everyone can do running half-assedly, but you need good technique to avoid permanent injury. I got permanent injury and squats compensate for this. I have an exoskeleton of muscles around my spine and knee now. I recommend cycling to beginners. Much harder to get an injury unless you like pedalling downhill (all the cases where I had an accident where while pedalling downhill).

But this post already looks depth-first while my escape from the black hole was breadth-first.

Music. I always liked music very much. Finding new music you like provides a short mood boost. I found funk. The trouble with music is searching for something you like requires time, and I need novelty constanty. But every little bit helps.

Friends. If you don't have friends, and it's safe to say I didn't 2 years ago, go somewhere where people with similar interests gather. I found a place where people play board games. A small monthly fee and you can play one of nearly hundred board games with other male nerds. Board games are similar to computer games, but thrive on innovation in game mechanic department. Very good if you like strategy games. Board games are the most refined kind of multiplayer game, they are designed to be finished in one seating and the better ones are built about interesting decisions. Unlike with modern multiplayer where you are shoveled around with complete strangers by a matchmaking system, you get to play with the same group. It's like dedicated servers are back ! Even better, only one person needs to own a board game. It's like StarCraft 1 multiplayer "Spawn" feature is back!! Also, you get to see and meet people, and disconnects are very rare because it's more awkward to disconnect from people you're seeing face to face. No one would like to play with that jerk again. Automatic self-moderation system ! No need to appoint moderators, referees or implement a voting system that 2 pals can abuse to kick you because you killed them, or that never gets through because it needs 50%+ people and they're happy you're stuck with a bad teammate because it will make them win.
I still don't have many friends, and I only really meet them every Wednesday - but every little bit helps.

Get out of your flat. Simply go for a walk and see a changing view instead of the same 4 walls. No need to talk to anyone. This always helped me for a short while. Every little bit helps.

Hypericum pills. Herbal meds that according to some clinical tests are as effective as synthetic meds, with much fewer side effects. Notably, they don't cloud your thoughts, which is important for a programmer. The one notable downside is phototoxicity. You want to stay away from sunlight, or you'll get permanent dark spots on skin. I accomplish this by covering my skin. I understand this is not an option in Australia, but every little bit helps. Note: for hypericum you want either pills, or oil/alcohol based extracts, because the key component doesn't dissolve in water. Don't waste money on "tea".

Reading books, watching a movie. There are times when my anxiety overpowers me and I can't even focus on that, but a good movie puts me in a good mood and I don't necessarily mean a movie with a good ending.

Meditation. Supposedly improves concentration, memory and stress resistance by 30-40%ish. Just what I need. I only recently started so it's hard to estimate if it's helping me, but it's free and harmless and easy. 2 times a day, 15 minutes. You simply go into standby mode, close your eyes, try to throw out all thoughts from your mind. In particular, don't think about the past and don't make plans. If you must focus on something, focus on the present, like your breath or sounds (but human speech is very distracting). Every little bit helps.

Merely reading about your condition can be helpful. I started to feel better and gradually solve my problems once I read a bit about my behavior and motivation. It's like some barriers fade away and you slowly start exploring areas of your life you've never tried, things you were too shy to try, etc. It takes time.

Tips on sleep: I have an alarm set to 23:00 every day. When it rings, I go to bed. Actually recently I started going to bed even earlier. Turn off TV if you have one, stay away from computer monitor, smartphones, tablets. There's something about the blue light they emit that makes people not realize how tired they are. When I go to bed, I read a book or a newspaper. This doesn't interfere with my natural exhaustion sensor and the extra mental fatigue helps me fall asleep faster. If I have insomnia and really can't fall asleep, I turn on the light and read. Then I try going to sleep 1 hour later or so. If you still can't sleep, just lie with eyes closed and try to relax. Lying with eyes closed will still make you much more fresh in the morning than going out of bed or watching something and pretending you had no rest.

Also, I don't remember the source, but a recent study I read about found that sugar intake makes you feel better in the short run but causes anxiety and depression the long run. Foul stuff!

To do all these things (acting is the hardest part of depression) I used observation and logic. Observation to identify activities that make me feel marginally better. Logic, to tell myself it will be worse if I never do them.
See, it's like the female zombie in Return of the Living Dead says. You don't eat brains to feel good. You do that to make the pain go away. Do tell yourself it will make the pain go away, just a little. Keep repeating that.