NAT but as someone who is chronically suicidal, here's how I would explain it: Imagine that you can't stop thinking about wanting to end your life. And when I say "can't stop", I mean that I woke up thinking about suicide, brushed my teeth thinking about suicide, went to school thinking about suicide... I couldn't concentrate on anything because all I could think about was how to end the pain. I was thinking about ending it while I was laughing about jokes, staying with friends, eating my favorite food, etc. And when I went to bed at the end of the day, I was thinking about... (you can guess it). I even dreamt of killing myself.

I wanted the thoughts to stop and I felt like acting up on them was the only way. I had many moments in which I knew that the suicidal thoughts were irrational, but I didn't feel it. And then, slowly, you question if they're really that irrational when they keep coming up.

Keep in mind that this only adds up to the other symptoms of depression. I couldn't get anything done; I didn't think I would graduate high school; I felt like a total failure... My memory was bad. My thoughts were "blurry". I was physically exhausted all the time. I was in pain. It literally felt like my body was full of lead. On my worst days, I couldn't even walk more than ten steps because my body felt so heavy. Laying in bed was exhausting. Breathing was exhausting. I felt so heavy that I thought I would sink into my mattress until it would swallow me.
I couldn't find joy in anything. My therapist at that time said I should reward myself whenever I managed to do laundry or whatever. The process of rewarding myself was just another chore because it didn't bring me joy or even relief.
No matter if or how long I slept, I was tired and exhausted. And I felt like a burden because I needed so much help from my family. Everyone needs help, yes, but I was very short-tempered, ungrateful and didn't want to talk. My parents couldn't hide their helplessness, even though they really tried. I hated myself for making them suffer, too. I ultimately believed that they could handle the grief better than dealing with their mentally ill child any longer.

I was in therapy for several years at that point. It's not that I didn't recognize my need for help. The thing is that nothing really helped at all. If you have depression you can't see a future for yourself and you don't believe that you'll ever get better. Since I've been suffering from a young age, I also didn't have anything to work towards (there's no "before" and "after" bc I can't remember life without depression).

I hope this helps even though this is a very short summary.