My goal was to write the guidebook I wish I had available to me when I was starting out as a junior researcher 25 years ago. While still an undergraduate student, I became interested in learning more about the affective changes that occur when people participate in physical activity. At that time, I had some elementary background in psychology but had not taken even a single course on emotional or affective phenomena for the simple reason that such courses did not exist back then, at least at the universities I attended. My knowledge about emotion was limited to the highly abridged summaries of the classic theories of William James and Walter Cannon contained in introductory textbooks.

Lacking background and guidance, I made every mistake imaginable. I used measures without knowing much about them and certainly without having a good grasp of their theoretical underpinnings or their relative strengths and limitations. I selected one measure over another on the basis of such profoundly naive criteria as their brevity or popularity. I measured one variable (e.g., emotion) but discussed my results as if I had measured another (e.g., mood). I measured only a small part of a domain of content (e.g., only a few discrete mood states) but my ignorance led me to generalize to the entire domain (e.g., the global domain of mood). I based my conclusions on measures that were deeply l awed although even a rudimentary psychometric analysis would have alerted me to this fact.