“What I term the existential vacuum constitutes a challenge to psychiatry today. Ever more patients complain of a feeling of emptiness and meaninglessness, which seems to derive from two facts. Unlike an animal, man is not told by instincts what he must do. And unlike man in former times, he is no longer told by traditions what he should do. Often he does not even know what he basically wishes to do. Instead, he either wishes to do what other people do (conformism), or he does what other people wish him to do (totalitarianism).”
— Viktor Frankl, The Will To Meaning (1969)
Take note that the feeling of emptiness described here by Viktor Frankl is quite different from the Eastern concept of 'emptiness'. According to Frankl, our main motivation for living is our will to find meaning in life. The experience of the existential vacuum results from this lack or loss of 'meaning'.
Most people — the ones who seldom do self-reflection — try to cope with the crisis by merely imitating the meaning/purpose that they see or hear from others, which often prove to be one-dimensional. These guys just want the easy way out; hence, they lose their freedom as it becomes easier for those in power to tell them what they should do (buy a house/car, vote, marry someone, have kids, get rich, pay your taxes, put up a business, etc.). On the other hand, there are others who conclude that life really has no meaning, hence they become nihilists who either live in seclusion or do all kinds of crazy stunts thinking that they are free to do whatever they want.
Indeed, entering this void is the most frightening thing that could happen to anyone; it can really suck the life out of you. That's why it's very important to think carefully about your ultimate purpose in life. Material, emotional, social, and intellectual pursuits are short-lived and temporary. Better to choose one which can never be taken away from you by anyone or by any circumstance — a spiritual goal, perhaps?