Unfortunanetly in todays world many people would consider themselves depressed. But they do and within depression many things happen. One thing that happens that is pretty interesting is when people have a depressive realism which is the tendancy of mildly depressed people to make accurate rather than self serving judgements, attributions, and predictions.
We see this happen a lot just after someone tries out for a sports team and gets cut or just after a young relationship ends. They are bummed out and depressed that things didnt work out as they hoped but in the end realize maybe they werent that good at the sport or activity or the relationship was not that great and there will be better out there.
I think a great example of this is my sister. She is a pheonominal soccer player and always has been but when she was younger she always did all the sports that she could. In her sophmore year her basketball tryout didnt go as she had hoped and she was bummed, but after talking it over with people and thinking about it rather than continuing to believe she was great at everything and have self serving judgements of her play she realized soccer was what she excelled and decided to focus on that. Since then she has done awesome and been able to put in more time and effort as she focused her actions. But it took a negative event to bum her out to make her thing a little more accuarately about the whole situation.
Becoming depressed is not a good thing but in the case of only mild depression if you have a moment of depressive realism it can allow you to have some accurate thinking moments that could really help you out in the long run. In no way shape or form is depression a good thing but a tiny positive could be this moment of depressive realism we all expierience in our moments of weakness.