James 4:6 (KJV) But he giveth more grace. Wherefore he saith, God resisteth the proud, but giveth grace unto the humble.
We can see that when we have a proud attitude we will find GOD resisting opposing us. Who would want that? It is better to then walk in humility as this will result in receiving grace from GOD.
Some definitions of grace in the Free Dictionary, that are relevant here, are:
4.a. A disposition to be generous or helpful; goodwill.
4.b. Mercy; clemency.

5. A favor rendered by one who need not do so; indulgence.

6. A temporary immunity or exemption; a reprieve.

8. Christianity
8.a. Divine favor bestowed freely on people, as in granting redemption from sin.
8.b. The state of having received such favor.
8.c. An excellence or power granted by God.
The Greek word that translated here to grace is defined as follows:
G5485 (Thayer) χάρις charis
Thayer Definition:
1) grace
1.a) that which affords joy, pleasure, delight, sweetness, charm, loveliness: grace of speech
2) good will, loving-kindness, favour
2.a) of the merciful kindness by which God, exerting his holy influence upon souls, turns them to Christ, keeps, strengthens, increases them in Christian faith, knowledge, affection, and kindles them to the exercise of the Christian virtues
3) what is due to grace
3.a) the spiritual condition of one governed by the power of divine grace
3.b) the token or proof of grace, benefit
3.b.1) a gift of grace
3.b.2) benefit, bounty
4) thanks, (for benefits, services, favours), recompense, reward

Therefore when we walk in humility we can be assured that:
He gives more grace.
He gives more ability and power in the way we ought to behave and walk.
He gives more ability to reflect Himself in life,
He gives more good will.
He gives more loving-kindness.
He gives more favour.
He gives more joy, delight, and so much more as we can see.
Because He gives more grace we then should submit ourself to Him as it is the prerequisite of victory over the devil. James 4:7 “Submit yourselves therefore to God. Resist the devil, and he will flee from you. ”
When we humble ourself GOD will lift us instead we lifting ourselves.
James 4:10 “Humble yourselves in the sight of the Lord, and he shall lift you up.”
Jesus Himself is the source of grace as we read in John chapter 1:
“John 1:14 (KJV) And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.”
“John 1:17 (KJV) For the law was given by Moses, but grace and truth came by Jesus Christ.”
Therefore let us encourage one another to always walk humbly before the LORD and each other.