Had there not been repentance, people would have been doomed. However, repentance is an aspect of Allah's Mercy upon us. Man should be certain that Allah the Almighty will forgive him his sins after he regrets them, quit committing them, and determines not to commit them again.

Hence sincere repentance has three pillars: regret, abandoning the sin instantly, and determination not to commit the sin again.

Dr. Umar Abdul Kafi:
 
There is one more point; which is giving people their due rights back. Rights are of two kinds: Allah's Rights and people’s rights

Dr. Rateb: 

Well, yes that is right. As you have just said, there are Allah's Rights and people’s rights. Actually, the rights of people are a very serious issue.

The prophet (PBUH) was called for the funeral prayer of one of his companion who passed away. People’s rights are not forgiven except by fulfilling them or being forgiven by the person who has a due right. The prophet (PBUH) asked:“Is he in debt?” They said: Yes. So he said:
"Then offer Salat for your (dead) companion." A companion said, "O Allah's Messenger! and I will pay his debt." So, he led the Salat (prayer). The next day, the Prophet (PBUH) asked him, "Have you paid his debt?" He replied, "No, not yet." The third day he asked him the same question and the answer was the same. On the fourth day the Prophet (PBUH) asked him, "Have you paid the debt?" He replied, "Yes, I have."  Then the Prophet (PBUH) said, "Now he can rest in peace.")

[Ahmad, on the authority of Jabir]

Dear sir, Allah forgives us if we fall short in fulfilling His Rights, and reconciliation with Him can be done in seconds. Hence, it is not hard to ask Allah sincerely for His Forgiveness and get it. However, sins that involve other people’s rights can only be forgiven if you fulfill people’s due rights upon you, or if they forgive you.