From the book Man's Search For Meaning by Viktor E. Frankl
As each situation in life represents a challenge to man and presents a problem for him to solve, the question of the meaning of life may actually be reversed. Ultimately, man should not ask what the meaning of his life is, but rather he must recognize that it is he who is asked. In a word, each man is questioned by life; and he can only answer to life by answering for his own life; to life he can only respond by being responsible. Thus, logotherapy sees in responsibleness the very essence of human existence.
This emphasis on responsibleness is reflected in the categorical imperative of logotherapy, which is:
"Live as if you were living already for the second time and as if you had acted the first time as wrongly as you are about to act now!"