The Training of the Will
by Roberto Assagioli, M.D.
1966

From the Introduction:

The wide gulf between the external and inner powers of modern man is the most important and profound cause of the individual and collective evils which hinder the progress and even menace the future of our civilization. Modern man has paid dearly for the external powers and advantages he has gained; while his life is richer, broader and more intense, it is at the same time much more complicated and exhausting. Its rapidly increasing pace, the countless enticements it offers, the complicated economic and social machinery in which it has enmeshed him, make ever increasing and more insistent demands upon his nervous energy, his mental powers, his emotions and his will.