This is your bedrock for all your finances. Without an emergency fund, any other goals you may have, such as investing or saving for a vacation or college, will get derailed. It's difficult to recover.
But first of all, have a budget and follow it. I'm retired now, but still use a budget. It's basic to sound financial planning and peace-of-mind.
Recent surveys indicate that 61 percent of American families cannot come up with $400 to meet an emergency. Don't be one of these people.