Is it really complicated ? Not really, but a lot of factors go into whether a person can be truly forgiven, or not.

A. Many accounts of such people in the Bible.
Blessed is he whose transgression is forgiven, whose sin is covered.
Psalm 32:1

B. They forgive and they do not dwell on the sins of others. Readiness to forgive
is an attitude which doesn’t dwell on other’s faults, but examines our own
relationship with God. God is ready to forgive…
For thou, Lord, art good, and ready to forgive; and plenteous in mercy
unto all them that call upon thee. Psalm 86:5

C. They don’t collect imaginary sins. Often people misinterpret the actions or words
of someone else. But if they are in a bad spiritual state they could quickly make
the wrong conclusions, and assume that someone sinned against them.
He that answereth a matter before he heareth it, it is folly and shame unto him.
Proverbs 18:13

Some people collect stamps, some people collect butterflies. Some people
collect what they view as offenses by other people. For instance: On a TV
commercial a man is starting to lose his hair. So everywhere he looks, he sees
balding heads. When he goes to the grocery store and sees a melon, he thinks
of his head being bald. When he sees the US Capitol Building, with it’s huge
dome, he thinks of his head without hair. WHY? He has internalized it – instead
of turning it over to God – so he becomes paranoid about everything people
say and everything he sees. When people aren’t right with God, nothing you do
will please them. If you tell them you appreciate them helping in some way,
they will interpret that to mean, “They want me to do it more.” If you don’t say
anything, they say, “They don’t appreciate anything I’ve done.”

A. It is needed only when a genuine offense is committed. Some people hate their
“brother without cause”.
Strive not with a man without cause, if he have done thee no harm.
Proverbs 3:30

For example: “I forgive O.J.” – Well, he didn’t do anything to you. So, how can
you forgive him? That’s like saying to a man whose mortgage payment was four
months past due – “Brother, I forgive you.” Unless you held the mortgage, what
good is that statement?
B. It depends upon true repentance.
Take heed to yourselves: if thy brother trespass
against thee, rebuke him;
and if he repent, forgive him. Luke 17:3

You have a Biblical obligation to tell him the fault face to face, not behind his
Moreover if thy brother shall trespass against thee,
go and tell him his fault
between thee and him alone: if he shall hear thee, thou hast gained thy
brother. Matthew 18:15

How can this be done, if the person you want to forgive is dead ?
– Get it right with God. If it even matters to the person, and they are in heaven,
there is forgiveness.
C. It depends on the willingness of the offended party. It is required when
conditions are met.
But if ye forgive not men their trespasses, neither will
your Father forgive your trespasses. Matthew 6:15

Many carry around bitterness and anger from years past. Tragic ! It affects
their health, their mental state, and their relationship with God. Even Christians
who carry grudges around, for even as little as a couple weeks can be
negatively affected.

*Many people want to forgive themselves. So what if you can forgive your own sin,
but don’t have the record of it taken away from heaven ?

Like a man robbing a store. He is caught, he goes to trial, and is found guilty. While
in jail, he receives a letter from the store owner. In it, the store owner says that he
has forgiven the man. So, what? It doesn’t get the man out of jail any more than
self-forgiveness will get you out of hell or a bad relationship with the Lord.

A. His forgiveness is real and lasting.
If we confess our sins, He is faithful and just to forgive us our sins, and to
cleanse us from all unrighteousness. 1 John 1:9

In whom we have redemption through His blood, even the forgiveness of sins:
Colossians 1:14