Is it better to be a specialist or a generalist designer?

The starter of a new year makes us reflect on what we plan to do next, personally and professionally.
In my case, I decided to go back to school and to find a new job. My previous contract wasn’t renewed, so I need to get back out there and sell myself as a designer. But how do I do that exactly? Should I keep pushing towards being the best generalist designer that I can be or do I need to specialize in a particular field?
What’s the difference between a generalist and a specialist designer and how do we chose between them?