The monograph includes the results of a 7-year study of proactivity. Proactivity is a fundamental part of human nature, and it contributes to optimal functioning in a changing society. The findings of the study are grouped into sections ranging from philosophical sources to psychotherapeutic applications. Extensive data are presented on mental disorders (schizophrenia, depression, anxiety, and drug addiction). Each article is supplied with an English title, abstract and keywords. Some results are written entirely in English. Also, a lot of materials presented previously never published. The book may be of interest to psychologists, psychiatrists, psychotherapists and philosophers.