Personal recollection will be given on the ways how the author had come to propose the mechanism of sudden stratospheric warmings published in 1971. In early days the author was considering possibility of an instability of "deformed" polar vortex as the cause of breakdown of the polar night jet and examined the possibility by use of barotropic model collaborating with Dr. Hirota. Then he was led to the necessity of extending the idea to instability of 3-dimensionally deformed polar vortices. Thus he started to obtain the "basic state" which includes stationary planetary waves forced from below, when he stayed at the University of Washington. At the same time he learned much from literatures by Prof. Reed and other authors treating evolutions of real events by data analysis and noticed that weakening of the polar night westerly jet accompanies the event. Since this might not be explained by linear instability, he started to look for a mechanism to cause westerly weakening. In this investigation the Charney-Drazin theorem provided a basis for searching an easterly acceleration mechanism. Earlier days the author once considered possible mechanism of easterly acceleration by equatorial Rossby waves owing to stimulation by Dr. Lindzen's arguments in the course of developing theories of QBO by him and Dr. Holton. Although the idea was not completed at that time it became the essential clue to find the mechanism in the case of mid-latitude Rossby waves. Through these considerations the cancellation of transport of physical quantities by eddies and that by the mean circulation was recognized and Lagrangian view of things emerged. In the author's view the concept "wave packet possesses and carries (angular) momentum in the direction of the wave propagation" was vaguely recognized by many researchers and it was a source of inspiration, at least for me, in those days. Soon after, the proof was given by Dr. Uryu for the case of Rossby waves and more general and rigorous proof by Dr. McIntyre and other authors came out a little later.