Careers rise and careers fall.
The trajectory of an executive's career is rarely a straight line of upward movement. Most have periods of plateaus, lateral moves and even temporary backslides.
The worst cases show a sharp drop into a deep valley of despair. Why does this happen?
In some cases it involves a cataclysmic event. A bad decision or lapse of judgement leads to a termination. Yes, that can be damaging but it doesn't have to completely ruin a career.
The majority of cases I've seen over the years involve simply being unprepared financially. A layoff thrusts someone into the job market unexpectedly and they have little to no savings to help them sustain through the time it will take to find a similar position.
Desperation begins to set in. They start targeting positions well below their level. If they land something just to pay the bills they aren't sure how to dig out and turn things around. If they don't land something quickly it could send them into a depression which only makes things worse and last longer.
Don't let the rock slide steam roll you into the gorge. Get some help. Break out of the spiral and begin the climb back to where you belong. Then, build the savings to make sure it doesn't happen again.