God created the universe and everything in it. If you do not yet accept this, see http://www.wiebefamily.org/e.htm for reasons why you should.
I am an engineer by profession. I design computer hardware. What I design, I do so according to a specific purpose, plan, and intent. My expectation is that it will function accordingly. I am, in essence, lord over my creation. If a piece of it does not function properly, as I have foreordained it to function, then without hesitation I rework it and debug it until it does, removing faulty components and aspects of the design, and replacing them with ones that work the way I have decided they should.
Likewise, it is important to realize that the God who created the universe is Lord over his creation. He designed it according to his own purpose, plan, and intent. What he defines as good is, by definition, good. What he defines as bad is, by definition, bad. It is his good pleasure to delight in the work of his own hands. We, the creation, have no intrinsic "rights" or freedoms that allow us to sit in judgment of God or even venture to bring into question what he defines as just vs. unjust, or good vs. evil.
After all things were created, the first man and woman were given instructions. They lived in a paradise, called the Garden of Eden. They were told by God not to eat the fruit of a particular tree. They disobeyed God and ate from it anyway. God's response was to banish them from the Garden, decree certain hardships upon them and their offspring, and curse the creation in which they lived. Although we don't understand the mechanism, the first man and woman became tainted with a propensity towards disobedience that their children would inherit from them throughout all the generations of mankind.
This is what we refer to as the fall of man. All men became sinners by nature and by deed, with no hope of redeeming themselves or rectifying the problem, apart from an act of God.
God's justice requires that no one with an unpardoned criminal record of sin shall ever stand in his presence. Instead, he has decreed that any and all such persons shall be forever banished from his presence, sentenced to eternal damnation in a place of fiery torment.
Don't like that? Deal with it. It's God's universe, not yours.
It is important that this baseline be established, which is that no descendant of man that has ever lived or ever will was worthy of receiving anything good, due to his natural and willful disobedience to God. Rather, it was each man's natural and default destiny to receive just condemnation and suffer eternal death and separation from God.
God provided the means of redemption, however. Although God's justice will not permit a sinner to stand in his presence, God chose to take on the sins of the world himself by sending his son Jesus to willingly suffer the punishment that we deserve. Although he himself never sinned, and was sinlessly conceived through an act of God himself, Jesus chose to suffer and die to pay the penalty for our sins.
Then, having paid in full the just price for our sins, he was buried in the ground. After three days and three nights, he rose up from the dead. His resurrection serves as proof to the world that he is who he said he was and did what he said he did. The empty tomb that had been sealed and carefully guarded under the power and authority of the Roman government (to prevent Jesus' body from being stolen to fabricate a resurrection) and his post-resurrection appearances to over five hundred of his disciples (who had nothing to gain and everything to lose by maintaining that he did in fact rise up from the dead) serve as proof of his resurrection.
"Grace" is getting what you don't deserve. "Mercy" is not getting what you do deserve. God cares enough to offer mercy and grace to those who would simply receive it. The sins of the world having been paid for, God's only requirement is that you recognize what would have been your otherwise hopelessly sinful condition and trust him, and him alone, resolving to believe that Jesus really did die for your sins and rise up from the dead.
The difference between what we call a "believer" and a "non-believer" is that the believer believes this, and the non-believer doesn't. Salvation is therefore 100% by faith in God.
You must resolve to believe this now, and continue believing it to the day of your death, after which God will call you to account. Your faith in Christ may bring to you great trouble in this lifetime (see my "no-nonsense" parody tract, "How to get your head chopped off".) On the other hand, it may not. In any case, those who believe the good news are pardoned, on account of what Jesus did on their behalf. They will inherit God's kingdom, restored to paradise, even though they did not deserve it, and live there forever. Those who do not believe will be condemned forever.
This is the bottom-line. The question is, what are you going to do about it? The issue is so profound that every other decision and every other pursuit of a man's life is rendered comparatively meaningless. Your choice is, more than literally, a matter of life and death.
Jesus is coming back. His coming will not be as it was the first time, to offer up his own life as a sacrifice for our sins. His second coming will be to summon the living and the dead who have chosen to trust in him, and execute terrible judgment on those who did not.
If you have any questions about the above, do not hesitate to ask.
Or better yet, get a bible and read it, like I did, and see for yourself the choice being set before you.
I grant this work to the public domain.