Proverbs 27:1,  Boast not thyself of tomorrow; for thou knowest not what a day may bring forth.

Boast means to inflate, to swell, to blow.

To brag, or vaunt one's self; to make an ostentatious display, in speech, of one's own worth, property or actions.

(Example: a blowfish that puffs himself up when facing danger, expands himself to appear larger than he really is so as to scare his adversary; the blowfish is boasting)

Demonstrate this verse with a balloon and a pin.

Blow up a "boast balloon." Bring in an unplanned pin (represents an unknown event of tomorrow) and puncture the balloon. Burst the boast!

The bigger the boast, the bigger the bang.

This demonstrates that today's boast about tomorrow does not take into account the "sharp pins" of tomorrow.

You do not know what "pins" there are that the day may bring forth.

Your boasting excludes the pins from your thoughts and imaginations and elevates you above the things that you might expect in this life.

What about the pin of lost opportunities,

the pin of rebellion against God's will,

the pin of sickness,

the pin of famine, the pin of death,

the pin of family problems

What about the pin of natural calamity,

the pin of economic downturns,

the pin of war,

so many pins beyond the control of the boaster.

Within the control of God, but the boaster is not God!

You can paint any picture you like about tomorrow. "What a grand and glorious tomorrow and I will be great in it."

Your imagination is free to conjure up images of yourself in tomorrow's scene.

James 4:13,  To day or to morrow we will go into such a city, and continue there a year, and buy and sell, and get gain.

You can easily inflate yourself, you can swell yourself, to anything you want to be, because you don't have to produce until tomorrow.

Boasting thyself means to view yourself in the tomorrows by magnifying yourself in a way that God reserves for himself to do for you if he so chooses.

The Bible says to humble yourself and God will lift you up.

Lifting you up, God reserves for himself and when you lift yourself up by boasting you take upon yourself God's role.

You become God in your life.

Tomorrow is not yours to inflate. Tomorrow does not belong to you. God gives you today. Only today is yours, not tomorrow.

Tomorrow is God's realm. Today and tomorrow is the present with God.

But we have no business wasting our today's by boasting of tomorrows that may never come.

Jesus said in Matthew 6:34,  Take no thought for the morrow: for the morrow shall take thought for the things of itself. Sufficient unto the day is the evil thereof.

Are you not busy enough for today? If you have time to boast of your tomorrows perhaps you need to work harder today!

This is the day that the Lord has made, let us rejoice and be glad in it.

We must wait until he makes the day and gives us the day for us to use it. We are not allowed to use tomorrows!