I think as far as ending its an individual thing. Some depressions might be lifelong depending on the causes. For me the causes were environmental so after I changed my environment it was more possible for me to heal but it still took a long time and I did it mostly on my own, spending time with the negative thinking and working through the puzzles of life. In the beginning I waited for it to clear on its own but I had no idea that it would be more than 30 years! I slowed the process down a lot by self medicating and working against myself. One thing I think was really important was to retrain myself in the language I used when self communicating. Negative statements only reinforced the negative cycle I was stuck in. Learning to feel genuine gratitude for the good things in my life slowly began to turn my momentum in a new direction but it still took a surprising amount of time to begin to feel confident that things could still turn out ok. I know how painful and lonely it can feel after a relationship breakup. Try not to overthink it if you can, make sure you spend a little time each day thinking about something positive, something simple, like the beauty of flowers or the cuteness of kittens, anything that might make you smile just a little inside. I know its hard but if you stick to it and give it time the table might start to turn. Again, it depends on the causes of your depression.