Do you think there’s hope no matter how desperate the situation is for a person?

What do you tell yourself when you’re having very dark thoughts and want to disappear? I would like to know how you do it and get through. These lasts days I’ve just been in bed and feeling awful. Intense hopelessness and very dark thoughts. I feel trapped, like I’m backed up into a cul de sac with only one thing to do. It’s frightening. Don’t know what to do...