What bible passages tell us If we must accept GOD'S GRACE when HE gives it to us?

Sin is defined by St. Augustine as factum vel dictum vel concuptium aliquid contra legem aeternam- any thought, word or deed against the eternal law of God. Sin is the turning away from God, our true end, and the fixing of the affections on something forbidden by the law of God.

That sin is a turning away from our true end, is well brought out by the Greek word for sin, hamartia, which means a “missing of the mark, a bad shot.”

Sin is possible because we posses free will, which we can abuse and turn against the purpose for which God gave it to us. There is much in our nature which we cannot change, such as our inclinations to pride and sensuality, our proneness to vanity, anger, sloth, obstinacy. All these things, which Scripture calls concupiscence, incite us more or less powerfully to sin. But in themselves they are not sinful for sin is all possible where free will comes into action. “If we look back over our past life, we shall clearly see the difference between impulses to sin due to our natural appetites, and certain thoughts, words and deed which me might have avoided had we so willed. Hence sin has its toots in the freedom of the will: it is a willful transgression of what we know to be God's will” (Pesch, The Christan Philosophy of life.)

There are no passages in Scripture which explicitly say that once offered God's grace you can then choose to reject it. I emphasise the word choose.This belief is called Arminianism, condemned as heretical by many Christian organisations but accepted by others such as Methodism.

In effect all accept grace (the truth about Christ being God) when offered (eyes opened to the truth).

Those who believe this strain of thought will cite where the bible repeatedly says "If today you hear his voice do not harden your heart." (Psalm 95, Heb 4) or Ezekial 18:23 "Have I any pleasure at all that the wicked should die? saith the Lord GOD: and not that he should return from his ways, and live?"

Some also cite 2 Peter 3 where it says:

“God is not willing that any should perish, but all should come to repentance.”

You must be careful to read these texts and understand to whom they are addressed as has been said 'a text without a context is a pretext for whatever we want to believe'

Hebrew

4:16 Let us have confidence, then, and approach God's throne, where there is grace. There we will receive mercy and find grace to help us just when we need it

Define God's Grace. (????)

I'm seriously lost here.