Make it a habit: whenever you see someone do something, ask yourself right away, "What is this person trying to achieve?" But start this practice with yourself first. Carefully examine your own motives in everything you do.
Use thyself; as often, as thou seest any man do anything, presently (if it be possible) to say unto thyself, What is this man's end in this his action? But begin this course with thyself first of all, and diligently examine thyself concerning whatsoever thou doest.