Praise be to Allah.
All praise be to Allaah for the great blessing which He has bestowed upon you by guiding you to the way of truth after you had been astray, and for your return to Him after you had been a sinner, neglecting His laws. We ask Him, may He be glorified, to complete His favour upon you by guiding you further and making you adhere steadfastly to His religion. As regards what you should do about your past and how you can make up for what you have missed, you will find detailed answers in the book “.."I Want to Repent, But...",
With regard to du’aa’s to do with repentance that you can recite every day and whilst at work, al-hamdulillah there are many such du’aa’s, among the greatest of which are as follows:
“Rabbi’ghfir wa’rham wa anta khayru’l-raahimeen (My Lord! Forgive and show mercy, for You are the Best of those who show mercy!)” [al-Mu’minoon 23:118 – interpretation of the meaning].
“Rabbanaa ‘ghfar lanaa dhunoobanaa wa israafanaa fi amrinaa (Our Lord! Forgive us our sins and transgressions (in keeping our duties to You).” [Aal ‘Imraan 3:147 – interpretation of the meaning].
Shaddaad ibn Aws (may Allaah be pleased with him) reported that the Prophet (peace and blessings of Allaah be upon him) said: “The best prayer for seeking forgiveness is to say: ‘Allaahumma anta rabbi la ilaaha illa anta, Khalaqtani wa ana ‘abduka wa ana ‘ala ‘ahdika wa wa’dika ma astata’t. A’oodhu bika min sharri ma sana’tu, aboo’u laka bi ni’matika ‘alayya wa aboo’u laka bi dhanbi, faghfir li fa innahu laa yaghfiru’l-dhunoob illaa anta (O Allaah, You are my Lord. None has the right to be worshipped but You. You created me and I am Your slave, and I am faithful to my covenant and my promise (to You) as much as I can. I seek refuge with You from all the evil I have done. I acknowledge before You all the blessings You have bestowed upon me, and I confess to You all my sins. So I entreat You to forgive my sins, for nobody can forgive sins except You).” Whoever says this during the day, having faith in it and dies before the evening comes, will be among the people of Paradise, and whoever says it during the night, having faith in it, and dies before the morning comes, will be among the people of Paradise.” (Reported by al-Bukhaari, 5831).
Abu Moosa reported that the Prophet (peace and blessings of Allaah be upon him) used to recite the following du’aa’: “Allaahumma’ghfir li khatee’ati wa jahli wa israafi fi amri wa maa anta a’lam bihi minni. Allaahumma’ghfir li jiddi wa hazli wa khata’i wa ‘amdi wa kullu dhaalika ‘indi. Allaahumma’ghfir li maa qaddamtu wa maa ajjartu wa ma asrartu wa maa a’lamtu wa maa anta a’lam bihi minni. Anta’l-muqaddim wa anta’l-mu’akhkhir wa anta ‘ala kulli shay’in qadeer ( Allaah, forgive me for my sin. My ignorance and my transgression (in keeping my duty to You), and whatever You know about me better than I do. O Allaah, forgive me for sins committed in earnest and in jest, by mistake and deliberately, and I have done all of that. O Allaah, forgive me for what I have done in the past and what I will do in the future, what I have done in secret and what I have done openly, and whatever You know about me better than I do. You are the One Who raises and lowers people’s status, and You are Able to do all things).” (Reported by al-Bukhaari, 5919, and Muslim, 4896. This version reported by Muslim).
Ibn ‘Umar reported that the people counted for the Messenger of Allaah (peace and blessings of Allaah be upon him) when he recited one hundred times in one gathering: “Raabi’ghfir li wa tubb ‘alayya innaka anta’l-tawwaab ul-ghafoor (My Lord, forgive me and accept my repentance, for You are the Acceptor of Repentance, the All-Forgiving).” (Reported by al-Tirmidhi, 3356. He said, This is a ghareeb saheeh hasan hadeeth). May Allaah bless our Prophet Muhammad.