God promised us eternal life and because we know that he does not lie there is no doubt that if we follow the path he asked us to choose, abide by his commandments and his teaching we shall experience eternity.
One of God’s first promise to us his that he told us that he loves us so much that he allowed his son to die and said if we believe in him, we shall have eternal life. John 3:16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
For those who doubted him or refused to believe in his words, he told them her in Matthew 25:46 And these shall go away into everlasting punishment: but the righteous into life eternal. So to seek and receive eternal life we have to obey the words and teaching of our Creator.
We are, warned in the book of Revelation 21:8 But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars shall have their part in the lake which burneth with fire and brimstone: which is the second death. God does not take kindly to people who commit the acts that he mentioned above, if we are to enter into his kingdom we must not commit any of those abominations.
The mercy God that we worship is allowing us to change our behaviour because he does not want to see anyone of us suffer. The message he gave us here in the book of 2 Peter 3:9 The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance.