In the first part of this work, COACHING, the author describes and discusses what coaching is and not is, and clarifies how coaching is being used in this manuscript. In the second part, PERFORMANCE PSYCHOLOGY, the author describes and discusses important psychological variables believed to most directly affect performance, such as self-efficacy, intra personal causal attribution, goal setting and self-determination. In the third part, STUDY OBJECTIVES, the author describes the study objectives for the five papers in this thesis. Further, in the fourth part of the work, METHOD, the author describes the empirical designs used for the different papers in the manuscript. Fifth, in THE SUMMARIES OF THE STUDIES, the author gives a brief summary of the five papers in this book. Then, sixth, DISCUSSION, the author discusses the findings in the different studies regarding the study objectives in this paper. Last, THE PAPERS, the different studies in the manuscript are presented. In the APPENDIX the author gives an account for measurements and questionnaires used in this work.