Come now, you who say, “Today or tomorrow we will go to such and such a city, spend a year there, buy and sell, and make a profit”; whereas you do not know what [will happen] tomorrow. For what [is] your life? It is even a vapor that appears for a little time and then vanishes away. James 4:13-16(NKJV)
The wisdom in not boasting about tomorrow is; you’re not all knowing – only God is. You do not know what will happen tomorrow but God does. But that doesn’t mean don’t have plans for tomorrow rather submit your plans to the God who knows tomorrow or even better still find out and follow the plans of the God who knows tomorrow. While you may not know what tomorrow holds the God who holds you also holds tomorrow. Get to know Him and you will know that your tomorrow shall hold more than your today.