Most of us have many phases to our careers, from the typical entry level jobs through mid-career to retirement. In the 20th Century, this seemed to run in a predictable series of stages, and often involved working for the same employer, in the same industry or profession, for decades. Not any more.
Now, it is becoming increasingly rare for someone to have a smoothly-continuous career with no hiccups or periods of unemployment. Layoffs happen. Employers restructure or are gobbled up by someone else who moves the jobs to another location or shuts down divisions or functions.