how to know that Allah had forgive all of our wrongdoings?

Bismillahirrahmanirrahim..

Assalamualaikum wbt.. Erm, someone had asked me this question and want me to answer it in my blog. I promise i'll try to answer it based on what i know and had learned. Actually i'm far from eligible to answer this question as i also committed sins that i feel like really ashamed of me by doing that things. But i promise to not doing it anymore and hope that everyone will forgive my wrongdoings to them.. :')

Repent to Allah.. This is how to repent to Allah. For repentance to be accepted by Allah, one should go through these four stages:

1. Stop the sin.
2. Regretting deeply and truly for the sin you have committed.
3. Return to Allah for forgiveness.
4. Strong intention to never return to that same sin again.
(Link)

If you have sinned to a person, it is compulsory for you to offer your apologies to him or her. Do supplicate (dua’a) constantly for Him to forgive you, insyaAllah. As for the matter on how to know that Allah has forgiven you… After committing a sin, a person who fears Allah and gave high respect to Him would feel a sense a despondency and despair thinking, “How will God forgive me for this sin?” However, it is noteworthy that despairing of God’s mercy in itself is one of the major sins in Islam for God is ever Merciful, ever Forgiving. (I’m afraid that the knowledge of if He forgives a sin or not lies with Him and only Him because only He knows what truly lies in a person’s heart, and the conditions he/she is in, but do remember that Allah SWT is “The All-Forgiving”  الغفار and do continue to repent). Do remember that He loves you and you’re not forgotten as long as you remember Him..

“And whoever does evil, or wrongs his own soul, but afterwards seeks Allah’s forgiveness, will find Allah is Forgiving, Compassionate.” (4:110)

By my constricted point of view, it seems that you have regretted of what happened in the past.. So, alhamdulillah for that.. :) For Prophet Muhammad, (peace be upon him) says:

"The one who repents from sins is like one who did not sin at all."

“No one sheds tears but Allah will save his body from the fire of Hell. If the tears trickle down a person’s cheeks, his or her face will be saved from any degradation. If one out of a group of people cries, the whole group will be blessed by Allah. Only tears have unrestricted power. Verily, tears can extinguish the fire of Hell."

But just think… what if you really did fatally hurt yourself (na’uzubillah minzalik)? You will never have the chance to repent, ever. In a way, you are very blessed.. :) You have been given a chance by Allah SWT to repent, to ponder over your past mistakes and learn from them, to be a better Muslim than before insyaAllah.

I know that this is very hard to do, but do remind yourself of what’s important whenever things didn’t go your way. There’s nothing wrong from remembering and learning from your past mistakes, but do not dwell on it until you became negligent and forget of what’s important. Be kind towards others, especially towards your parents. Even a smile is considered a good deed and is the simplest sunnah.. :) 

Do remember that all the calamities and difficulties that has been set for us has its own reasons, for He knows what’s best for us.. He knows better than us..

When Allah tests you, it is never intended to destroy you. When He removes something in your possession, it is (only) in order to empty your hands for an even greater gift.
- Ibn Al-Qayyim-

Remember your loved ones, recall all those blessings Allah has bestowed upon you all your life; a breath of life, a scrape of food, an opportunity. Remember the little things that matter to you. Appreciate and love these moments that you have had to chance to experience in this world, but of course, do not get attached to worldly matters that often until we forget to care for our fate in the Hereafter, because it is much much more certain than life.

Thanks again for the message, it made me realize some things that I have forgotten and negligent about… I hope and wish you all the best, insyaallah. Do take care dear, and be strong, okay? :)

The Prophet Muhammad SAW (peace and blessings of Allah be upon him) said: “Every son of Adam makes mistakes, and the best of those who makes mistakes are those who repent.” (Reported by Al-Tirmidhi)

*** Do read this wikipedia page on the concept of Allah’s forgiveness which explains why that there are so many attributes that deal with the subject of Allah’s forgiveness.

p/s; Allah never leave us.. For His loves to us is more than a mother's love to her child. :') May Allah bless!

All faults of my answer is entirely from me and the good comes from Him and Him alone. And Allah indeed knows best. To those who had read this and feel that something’s amiss or wrong; please point it out to me. Thank you so much, may Allah reward your effort greatly.