It's a question many people don't like to think about, but it is the single most important question you will ever face. Mt. Everest is the highest mountain on earth, with an elevation of 29,028 feet. There is a big difference between hoping you will go to Heaven, and knowing with absolute certainty that you will go to Heaven.
People have a tendency to compare themselves to one another.
A good law-abiding citizen who gives to charity and goes to church every Sunday looks pretty righteous compared to a serial killer. In the Garden of Eden, when Adam disobeyed God and ate the forbidden fruit, SIN entered the world. It is human nature to sin. As a result, except for Jesus Christ Himself, every single person who has ever walked the face of the earth has sinned. It only takes one sin-one time to tarnish our record, making it impossible for us to ever meet God's standard of perfection by our own merit.