In Man's Search for Meaning, Viktor Frankl says that people should not keep asking what the meaning of their life is or what the meaning of life is more generally. Instead, they should act as though life is questioning them, and they have to answer, illustrating the meaning of their lives with their actions. This idea of taking responsibility for the meaning of your own life is the essence of Frankl's philosophy of logotherapy. Having stated this principle, Frankl continues:
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!'
This reflection, he believes, will always lead the subject to act responsibly, since it involves imagining that the present is past, and the subject already has to live with the consequences of the thing they are about to do. This causes them to think about the finality of the action, contrasting this with the finite nature of their life, in which they will continually reap the consequences of bad decisions.
The categorical imperative of logotherapy might, therefore, be expressed more prosaically as having foresight, anticipating the consequences of one's actions. Frankl however, decides to give his central idea this concrete Nietzschean formulation to stress how final and irreversible the consequences of the action will be once it is taken and to clarify the precise mental processes that should precede it.