I struggle to forgive myself for the harm I have caused others in the past. If Allah is so merciful, why do I still carry this heavy guilt?
The weight you are carrying is real, and I understand why you carry it. Somewhere inside, you feel that if you stop punishing yourself you are treating the harm lightly. But guilt was meant to be a doorway, not a dwelling. It knocked so that you would turn back and mend what could be mended. You heard the knock and you turned. Sitting on that doorstep now repairs nothing, not for them and not for you.
Hear how your Lord speaks to the very ones who believe they have gone too far:
“O My servants who have transgressed against themselves, do not despair of the mercy of Allah; indeed Allah forgives all sins.”
Qur’an, Az-Zumar 39:53 · meaning
Notice that the fault did not break the relationship. He still says “My servant”. And He does not say some sins; He says all. If He is willing to release you, then keeping yourself in a prison He has already unlocked is not humility. It is an old habit of the heart that has not yet been told it is free.
And the mercy itself is of this nature:
“Allah is more merciful to His servant than a mother is to her child.”
The Prophet (peace be upon him), Sahih Muslim (2754) · meaning
A mother does not wait for her stumbling child to become perfect before she opens her arms. She reaches for him in the falling. Those who sit with wounded hearts see the same thing: a person is not freed by endless self-punishment. He is freed by making honest amends where amends are still possible, and then finding the courage to accept mercy. So where you can still repair something with the people you hurt, repair it gently. Where that door is closed, pray for them. After that, the sorrow has finished its work and should step aside.
“My mercy encompasses all things.”
Qur’an, Al-A’raf 7:156 · meaning
All things. There is no corner of your past that this mercy has not already reached. You are not asking Allah to make an exception for you. You are only being asked to trust a mercy that was there long before your guilt was.
One small step: Tonight, place your hand over your heart and say once, slowly, “O Allah, I accept Your mercy over my past,” and let that be enough for today.