The parable confirms that a saved/forgiven person has eternal security in the knowledge that we persevere to the end because our salvation is not dependent on our works.
The parable was not a commandment to forgive our fellow servants, because we know that we break all of Gods commandments. The commandments were not given as a condition to salvation, they were given to show us that we can't keep one single commandment. That's why Jesus had to keep them on our behalf.
Every single person has broken every single one of Gods commandments, there's no getting around that fact. And being born again, doesn't mean that we stop breaking the commandments. We still sin everyday for the rest of our lives, only a liar would deny that fact. But thank God His Son paid for every sin from our past and every sin we commit today and every sin which we will commit in the future. So Christ paid for all of the past, present and future sins of His people.
If salvation was dependent on anything we do, then nobody could be saved, because we sin everyday and it's not possible to live a sinless life, even with the help of the Holy Spirit.