Since you threw the challenge at me, I'll try to explain why it's just not that simple, as briefly as possible.Not sure i'll ever understand depression
Too much of a realist, I guess
If something in your life makes you unhappy, stop being involved with wtf ever it is. Problem solved.
The majority of clinical depression -- as opposed to situational depression -- stems from either chemical imbalance (not just neurochemical imbalance, but also hormonal imbalance, including low thyroid, low testosterone, etc.), or as a result of trauma (it often goes hand in hand with PTSD).
IOW, you can't walk away from whatever is grieving you, because the grief is part of you. You take your prison where ever you go. You can kid yourself, hide in drugs or alcohol, pretend everything is okay by losing yourself, but it lurks, like a mental herpes, waiting to break out again.
It's not "unhappiness", it's more like "what's the fucking point to anything?" combined with utter exhaustion, a total lack of enthusiasm, hope, joy, passion and even physical aches and pains. It's like having the flu, 24/7, for months or years at a time. At least that's how crummy I've felt and I don't have it severely.
/soapbox