You are asking about the doctrine of predestination. What does the Bible mean by the concept of "predestination." Do we really have free-will or are we mere players acting according to a pre-defined script?
This classic "predestination" puzzle led John Calvin to invent the idea that salvation is merely a matter of Divine selection and we are just pawns in the Divine Sovereign's cosmic chess game. He claimed that no matter what we do, right or wrong, good or evil, the outcome of our lives in terms of either salvation or condemnation has been fully determined before we were born.
If that's the case, what does it matter what one actually does? In my humble opinion Calvin was spouting nonsense (Romans 1:22; 1 Corinthians 3:19; 2 Corinthians 1:12). This idea makes a mockery of free will. It also makes a mockery of the notion of salvation by faith and the need for living a life in obedience to God's will.
The real question is, does God's foreknowledge predefine our actions? An analogy might help. You are a time traveler and a fan of horse racing. You travel to the future to learn that the horse "Speedy Gonzales" wins the 2012 Kentucky Derby and a number of other races preceding it. You then return to 2010 and start betting on "Speedy" in the races you know he's going to win.
Who caused "Speedy" to win those races? Did you, just because you knew he would win? Or did you know that "Speedy" would win because that's what he actually did? Surely it is because that's what Speedy actually did.
So it is with God's foreknowledge about our lives and their eventual outcomes in terms of salvation. Just because God knows how your life will turn out doesn't mean that He caused it to turn out that way. The only reason He knows that it will turn out the way it will is because you caused it - your decision determines your destiny not the other way around! So, it does matter what you do.
The two Biblical cases usually cited in terms of predestination arguments are Pharaoh in the time of Moses and Judas who betrayed the Lord. Those who believe in predestination cite the verses that say "God hardened Pharaoh's heart." They say that poor old Pharaoh was doomed before he was born. Not so. A careful reading will show that Pharaoh continually hardened his own heart before God closed the door on him. Likewise with Judas. He did what he did not because God forced him to do it but rather God knew beforehand that Judas would make the choices he made. Judas was responsible for what he did, not God.
It is true that, in ways we will never understand this side of the Kingdom, that God used His knowledge of Judas to integrate him into His plan but it was only because God knew that Judas would make the choices he eventually made of his own free will that he was used to further God's plan. Would Judas have been forgiven if, instead of hanging himself, he had gone back to the Lord after his resurrection and thrown himself on his mercy? Indeed he would have and we would have used him ever after as a shining example of God's wonderful mercy and love towards those who are truly repentant. Sadly, that was not the choice Judas made and he has gone down in history as a villain, a thief, and a coward, his name synonymous with betrayal. But these choices were made by these men. God did not force Pharaoh and Judas to do what they did.
Look at 2 Peter 3:9 - "The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish but that all should come to repentance." God does not reject anybody out of hand. He does not predestinate anyone to destruction. He desires EVERYONE to come to salvation. Sadly, few choose to do so. Peter's statement would be untrue if God had aribitrarily chosen people for damnation no matter what they do. He knows who will succeed and who will not. He has already read the script of your life but the key point is that He didn't write it. You did! So, make sure you write well!
The bottom line answer to your question is that it is not possible for God to reject you because of an arbitrary decision He has made. Such a decision will be based on your actions, not on His. In Acts 17:30 Paul tells the Athenians that God has commanded "all men everywhere to repent." Why bother with that if the decisions regarding salvation and rejection have already been made? Jesus said, "Fear not little flock, it is your Father's good pleasure to give you the kingdom." If we will follow him in faith and obedience, and depend thankfully on His grace, we will, in spite of our weakness and spiritual setbacks, be welcomed into the Father's kingdom when Jesus returns.
Here's another example from scripture - Genesis 18:17-19 "And the LORD said, Shall I hide from Abraham that thing which I do; Seeing that Abraham shall surely become a great and mighty nation, and all the nations of the earth shall be blessed in him? For I know him, that he will command his children and his household after him, and they shall keep the way of the LORD, to do justice and judgment; that the LORD may bring upon Abraham that which he hath spoken of him."
God's special relationship with Abraham was based on what Abraham actually did. The only reason God knew that Abraham would be faithful is because Abraham WAS faithful. What he actually did was the basis of God's foreknowledge. If Abraham had failed miserably, then that is the data which would have informed God's foreknowledge.
Your life is not unfolding due to a pre-arranged script. It does matter what you do. In living your life faithfully or unfaithfully, you are providing the data for God's foreknowledge. God is not writing the script of your life; you are. God is only reading what you have written, so, as we said before, write well!
I hope you have found this helpful.