I can immensely relate to this. Though I do experience more small rollercoasters, but those are all part of a bigger picture, a downward spiral I've been on for some time. I've noticed people talking about crisis, stories of people reaching the "crisis point". While I'm slowly breaking apart inside in front of observing eyes, I even talk about what I feel inside and still it seems that the only reaction is my own echo.
Maybe I do think for a moment that I'm in crisis, while feeling the torture of drowning inside, but there is no water to prove it. I eventually stop crying. I eventually stop my suicidal fantasies. I eventually do get out of the bed. At one point, every time.
I have been "functional" up until now. What people reflect back to me is that I still am. I can't work or think though. But I can pretend somewhat still, I don't even get it
I'm being dragged around in life through my reflection in others' perceptions. Am I not allowed to be in crisis or am I still "strong" enough?

Someone said that the "rock bottom" is an illusory concept. So maybe I'm too stubborn to evoke it while some aren't...