Every Christian should carefully consider the warning Jesus gave in His parable on forgiveness in Matthew 18. He is answering Peter's question about how often Peter should forgive others, and extends the answer with a parable showing that those who have had much forgiven can lose that forgiveness and face torment instead.
21 Then came Peter to him, and said, Lord, how oft shall my brother sin against me, and I forgive him? till seven times?

22 Jesus saith unto him, I say not unto thee, Until seven times: but, Until seventy times seven.

23 Therefore is the kingdom of heaven likened unto a certain king, which would take account of his servants.

24 And when he had begun to reckon, one was brought unto him, which owed him ten thousand talents.

25 But forasmuch as he had not to pay, his lord commanded him to be sold, and his wife, and children, and all that he had, and payment to be made.

26 The servant therefore fell down, and worshipped him, saying, Lord, have patience with me, and I will pay thee all.

27 Then the lord of that servant was moved with compassion, and loosed him, and forgave him the debt.

28 But the same servant went out, and found one of his fellowservants, which owed him an hundred pence: and he laid hands on him, and took him by the throat, saying, Pay me that thou owest.

29 And his fellowservant fell down at his feet, and besought him, saying, Have patience with me, and I will pay thee all.

30 And he would not: but went and cast him into prison, till he should pay the debt.

31 So when his fellowservants saw what was done, they were very sorry, and came and told unto their lord all that was done.

32 Then his lord, after that he had called him, said unto him, O thou wicked servant, I forgave thee all that debt, because thou desiredst me:

33 Shouldest not thou also have had compassion on thy fellowservant, even as I had pity on thee?

34 And his lord was wroth, and delivered him to the tormentors, till he should pay all that was due unto him.

35 So likewise shall my heavenly Father do also unto you, if ye from your hearts forgive not every one his brother their trespasses.
If the grace of Christ that we once received is to remain effective in us, if we are to preserve the confidence of salvation that we once had, we must endure to the end in following Christ and loving and forgiving others.

Growing in such love and charity is one of the essential steps "to make your calling and election sure" and to ensure that our forgiven state is not "forgotten," according to Peter in 2 Peter 1:
2 Grace and peace be multiplied unto you through the knowledge of God, and of Jesus our Lord,

3 According as his divine power hath given unto us all things that pertain unto life and godliness, through the knowledge of him that hath called us to glory and virtue:

4 Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust.

5 And beside this, giving all diligence, add to your faith virtue; and to virtue knowledge;

6 And to knowledge temperance; and to temperance patience; and to patience godliness;

7 And to godliness brotherly kindness; and to brotherly kindness charity.

8 For if these things be in you, and abound, they make you that ye shall neither be barren nor unfruitful in the knowledge of our Lord Jesus Christ.

9 But he that lacketh these things is blind, and cannot see afar off, and hath forgotten that he was purged from his old sins.

10 Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall.

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