I believe you are taking good mental balance for granted.
Remember that 'you' are running on top of a very complex biological computer consisting of billions of neurons, with hormones and other chemicals influencing its operation. It needs to constantly be supplied with nutrients and oxygen to function at all.
Sanity is actually a finely balanced thing. You need to worry about the appropriate things, but not too much, and not too little.
Little tweaks to neurotransmitter levels can have enormous effects on your cognition.
Edit: in addition to what the OP had said, also remember this: When you are well and truly depressed, you don't even want to get better. You don't want to feel good. Some part of you is fine with pain and suffering, and more pain and more suffering.
Remember that 'you' are running on top of a very complex biological computer consisting of billions of neurons, with hormones and other chemicals influencing its operation. It needs to constantly be supplied with nutrients and oxygen to function at all.
Sanity is actually a finely balanced thing. You need to worry about the appropriate things, but not too much, and not too little.
Little tweaks to neurotransmitter levels can have enormous effects on your cognition.
Edit: in addition to what the OP had said, also remember this: When you are well and truly depressed, you don't even want to get better. You don't want to feel good. Some part of you is fine with pain and suffering, and more pain and more suffering.