According to the humanistic-existential model, what is the key to a fulfilling life?

Taking responsibility for one's existence

The humanistic-existential model focuses on broader aspects of human existence. Humanists believe that human beings are born with a natural tendency to be friendly, cooperative and constructive, and are driven to self-actualise, i.e. to fulfil this potential for goodness and growth. Existentialists believe that from birth we have total freedom to give meaning to our existence or to avoid that responsibility. Those who shirk from this responsibility would live empty, inauthentic, and dysfunctional lives.