It's such a delicate balance. We also know that whatever we give our attention to thrives and grows and gains power. I guess in the end it is a choice we make - how long to sit and listen and learn, and when to open the curtains and choose to allow the sunshine in.
For some people, it never passes. They listen, engage and wallow in & with that pain until they drown. It's a tough call. I say that having had my lover commit suicide from depression 18 years ago.
Each one of us finds our own way. Or not.
Sad for those who never find the inner tools to get out. Good friends of mine included.. You are right - it doesn't always pass. Even more reason to pass over 'this too shall pass' if it doesn't seem to serve. Sometimes advice is little more than sentiment.
And gosh yes - always fling the curtains open, even if we would rather wallow.