This Shadow Life - Why are we Different?

Life is hard. That's true for everyone who has ever lived, and everyone who will ever live.
Every person suffers pain. Death, loss, and disappointment are experiences common to all people.
But we don't all experience depression or suicidal thoughts.
So what's different in those of us who do? What is the difference between the people who are sad for the appropriate amount of time and then move on with their lives, and the rest of us?
Are we broken from the start, down to the very core?

I don't think so.
We are different. That's all.
We might have been normal at one point, but then some trauma happened and pushed us over the edge. I wasn't normal. Never. I might have seemed normal, or at least, not strange enough to raise concern, but I wasn't really. There was always something fundamentally different about me.
Then the trauma happened and I things changed. My world was destroyed and suddenly it became glaringly obvious that I wasn't like everyone else. My reaction was all wrong.

For me, and for many other people I have talked to who suffer depression, we feel like we deserve the pain that we experience. We deserve to suffer and live some half dead version of life.
When we experience some traumatic event, we direct the pain inwards on ourselves.  We accept the pain because we think we deserve it. We welcome it. We blame ourselves for whatever happened to get us to that point.
In some cases we will even do things to make our suffering worse, to inflict more damage and destroy the pieces that are left of our lives.
For many of us, we don't feel that we deserve happiness, or health, or comfort. So we sabotage any chance that we may have of living a 'normal' happy life. This in turn makes us feel worse. We hurt people that we care about and damage anything we come in contact with. Then we feel worse about ourselves, less deserving, and we ruin more and more of our lives in some horrible vicious cycle of self destruction and depression.

We also inflict more pain on ourselves because we need it.
After a while the pain  or the emptiness left in its wake feels like home. We need it to survive.
Often our trauma comes from loss. The loss causes pain, but as the pain fades we begin to feel that we are losing our connection to that moment, that moment of feeling and connection to someone and something that was most important to us. We inflict further pain on ourselves to renew the connection. The regain the feeling that connects us to the most important moments in our lives.

We are not broken in the beginning, we are just people who interact with the world differently. Everyone experiences pain, and loss, but when we feel these things we reflect them inwards onto ourselves.
We blame ourselves, we punish ourselves.

I'm not sure what the message behind this post is. I'm not sure that anything can be done to  change the way we are, the way we react, the way we feel. I just want to help you understand what it is like for me, so that maybe you can better understand yourself, or the people in your life who are experiencing depression or suicidal thoughts.