I'm sorry you went through that. If I can ask a question, though: during that depressive dark night, would it have been helpful for someone to tell you to just let your bad feelings go? Is that something you would have told your friends when they were going through such a difficult time?
Positivity in and of itself isn't a bad thing at all. But it can become toxic when it's forced or when it's used to invalidate normal, human feelings. Having a positive outlook is great, generally, but it can go too far. When we're only focused on the light, we ignore the shadow that is just as much a part of ourselves.