I think often people who don't have experience with mental illness think that depression is about being sad. I would say that it's more about pain. Excruciating mental pain that often spills over into the body as well. Like a blistering burn, it makes you so sensitive that even the slightest external prodding feels like agony.
When I'm depressed, people hurt. Even if it's unintentional and well-meaning, people's words and actions sear into my fragile, blistered mental skin. It makes me want to hide permanently in a solitary cave. I can't be hurt if I don't let anyone in, right? Yet as safe as that cave feels, the isolation also hurts.
When suicidal thoughts have arisen in the past, it's always been about seeing no other escape from the pain. The pain of depression that is resistant to treatment, the pain of not knowing when, if ever, I will be able to feel happy again.
But just when it seems like the pain is unbearable, a ray of light will shine through the dark clouds. Quite literally that has happened outside my window as I right. And those rays of light are what help me to keep going.