For the meaning of life differs from man to man, from day to day and from hour to hour. What matters, therefore, is not the meaning of life in general but rather the specific meaning of a person’s life at a given moment. – Viktor E Frankl
The heart of this rule is to always be in the moment. Tomorrow does not matter, and yesterday is gone. Even each individual moment in the day, the one being experienced Right Now is more important than any of the rest.