In Shantung Compound: The Story of Men and Women Under Pressure, Langdon Gilkey wrote the following (pp. 193-94),:
Let us take it [meaning in life] to refer simply to a sense of worthful purpose in what we do and the life 
we lead. A man possesses a sense of "meaning" when he feels there is a vital connection between the goals he values and the activities and relationships in which he is involved.
Then what he does each day becomes a coherent means to ends he really prizes, his life and work accomplish something of value to him and so "make sense." Consequently his energies and powers are called forth in creative effort; he is vigorous, hardworking, and, in the good sense of that word, ambitious. In this sense, meaning in life is the spiritual fuel that drives the human machine. Without it we are indifferent and bored; there is no ambition to work, we are inspired by no concern or sense of significance, and our powers are unstirred and so lie idle. Without "meaning" we are undirected and a vulnerable prey to all manner of despair and anxiety, unable to stand firm against any new winds of adversity.
Then what he does each day becomes a coherent means to ends he really prizes, his life and work accomplish something of value to him and so "make sense." Consequently his energies and powers are called forth in creative effort; he is vigorous, hardworking, and, in the good sense of that word, ambitious. In this sense, meaning in life is the spiritual fuel that drives the human machine. Without it we are indifferent and bored; there is no ambition to work, we are inspired by no concern or sense of significance, and our powers are unstirred and so lie idle. Without "meaning" we are undirected and a vulnerable prey to all manner of despair and anxiety, unable to stand firm against any new winds of adversity.
Me: Shantung Compound remains one of the top 10 most insightful books I have ever read. I first read it years ago. It's the true story of men and women from all walks of life interned in a Japanese prison camp durng World War II. One won't find a better exposition of "lived" psychology, sociology, philosophy, anthropology and morality anywhere-- better than textbooks!