As a young man Thang Tong Gyalpo was reputed to perform miracles to make some of his points (and was apparently asked to stop doing so). How did he develop these siddhis? He could apparently perform miracles at will. Does the Stearns biography/hagiography or other source mention specifically how Thang Tong Gyalpo developed this ability?
Kirt's Tibetan Translation Notes
"Even if you practice only for an hour a day with faith and inspiration, good qualities will steadily increase. Regular practice makes it easy to transform your mind. From seeing only relative truth, you will eventually reach a profound certainty in the meaning of absolute truth."
Kyabje Dilgo Khyentse Rinpoche.
"Only you can make your mind beautiful."
HH Chetsang Rinpoche