"Boast not of tomorrow, for you know not what any day may bring forth" (Proverbs 27:1).
Brethren, let us not boast of that which is not in our power. The Lord has placed the times and the years under His power and He disposes of them. Only God Himself alone knows whether tomorrow's day will number us among the living or the dead. Some have died on the eve of their marriage; again, others have descended into the grave on the eve of their coronation with a royal diadem. Therefore, let no one say that tomorrow will be for me the happiest day of my life; tomorrow, I enter into marriage! Or, tomorrow I will be crowned with a royal diadem! Or, tomorrow I am going to a great feast! Or, tomorrow a great gain is coming to me! O, let no one speak of the happiness of tomorrow's day. Behold, yet this night your soul may depart your body and tomorrow you will find yourself surrounded by black demons in the tollhouses [Mitarstvo]! And yet, even this night, a man can be separated from his relatives and friends, from wealth and honor, from the sun and the stars and find himself in a totally unknown company, in an unseen place and at an unexpected judgment.
Instead of boasting of tomorrow's day, it would be better to pray to God to "Give us this day our daily bread." Perhaps today's day may be our last day on earth. That is why it is better to spend this day in repentance for all our past days on earth rather than vainly fantasizing about tomorrow's day, about the day which perhaps will not dawn for us. Vain fantasizing about tomorrow's day cannot bring us any good, but repentance for one day with tears can save us from eternal fire.
O righteous Lord, burn up the insane vanity that is in us.
+To You be glory and thanks always. Amen.+
From Prologue of Ohrid by St. Nicolai Vilimirovich