Do you think Jesus is saying we must forgive everyone for everything, lest we fail to forgive just one and are never forgiven by God for our momentary lack of forgiveness?
In order to understand, it is important to come to a knowledge of just how sinful you have been, are being, and will be throughout your life. Then understand that the penalty for that sin before a just Judge is death and eternal separation from the God who loves you. Contemplate how much you are loved by the just Judge in that He sent His only begotten Son to pay the entire penalty for your sin, (and not yours only but for every sin of all mankind throughout the ages) in order to reconcile you to also be a son of God and joint heir with Christ to all God has planned for you throughout all eternity.
Then realize that every sin is forgiven man except blasphemy of the Holy Spirit (unbelief). Free will is given us by God to choose Life or choose Death (Deuteronomy 30:15-20) and scripture even gives you the right answer for this multiple choice quiz --- Choose Life!
Now come to the brilliant deduction that in order for you to follow in the footsteps of the Messiah, you must leave all judgment to the just Judge and not take vengeance upon those who sin against you, but forgive them that debt as you have been forgiven your debt for sinning against our holy God.
Forgiveness implies that you will leave all judgment up to God for those who sin against you. After all, God knows all the details of the whys and the wherefores of each man's heart. You don't. So how can you judge a man's sin rightly?
Forgive them, and trust God to make all things right (Romans 8:28) in His perfect timing. And believe me, He will make all things right in His perfect timing!
Or choose death, if you wish to exercise your right to be the captain of your own soul.
It's the most important decision any of us can make.
And know this, forgiveness on your part toward a fellow man does not mean reconciliation with that fellow man. Reconciliation takes place only if there is repentance unless you just like to be a doormat to those who would abuse you ad nauseum.
You've been given many good answers and there does not seem to be much understanding on your part of this process of forgiveness even so. Have you ever actually placed your faith in Jesus? Once a person faithes on Jesus, the Holy Spirit indwells and begins to work progressively to teach, convict (of personal sin), discipline, and mold that believer into the likeness of the Son,
If you believe, then He who began a good work in you will be faithful to complete it!
Hebrews 12:2
Philippians 1:6
Go to GotQuestions, a link provided right here on Talk Jesus, and ask questions there about all these things. Read the answers until you understand. Read your bible in context, not just isolated scriptures. The Holy Spirit will do His job if you are open to His leading.