Your crisis happens because the challenge and the goal are gone.
If you just broke up with your partner, it is a whole side of your life which is gone.
The moment this happens, your relationship goals collapse and you end up in an emotional no man's land where the vision you had is no longer valid.
If you want to reawake your passion, you need to find new life targets.
It could be a new relationship or other life goals in which you invest for a while.
If you get fired, it is the same dynamics.
You loose your job and with it, you loose part of the vision for your life as well.
The targets you had simply collapse.
It is your whole emotional investment into that professional position which needs to be reinvested somewhere else..
What you miss is the energy associated with your goal.
If you face a crisis of meaning, it means that your past goals are no longer valid, or that you need new targets.