God says
O you who believe! Remain conscious of God; and let every human being look to what he sends ahead for the morrow! And [once again]: Remain conscious of God, for God is fully aware of all that you do! -- Q.59:18
Only firm belief in God and in that He is aware of all that we think and do, and firm belief again, can keep us on guard and be critical of our thoughts and our actions. He says, “whether you bring into the open what is in your minds or conceal it, God will call you to account for it”(Q.2: 284). The Prophet had said, ‘God will not look upon your forms, nor upon your deeds, but will look into your hearts and your intentions’. He even said. ‘Niyat-ul-momin khair-um min ‘amlehi’ i.e., the intention of the believer is better than his action!
And [always], O you believers – all of you – turn unto God in repentance, so that you might attain to a happy state!* -- Q24:31(last sentence)
*The implication of this general call to repentance is that since “man has been created weak”(4:28), no one is ever free of faults and temptations – so much so that even the Prophet used to say, “I turn to Him in repentance a hundred times every day” -- (Ibn Hanbal, Bukhari and Bayhaqi, all of them on the authority of Abd Allah ibn ‘umar).
The following is recommended in view of the above:
(1) Very brief calls to repentance.100 times each morning and evening. If you can’t, then you may do one in the morning and the other in the evening.
“Subhan Allahi wa bihamdihi, astaghfirullah, wa aatoobo elaiyh”.
“Rabbighfir warham wa anta Khair- ur- Rahemeen”.
(2) Include in your supplications after every Farz prayer:
Alla-humagh-firli wale-waledayya wa le jamee-il momeneena wal momenaate wal muslemeena wal muslimaatin al-ahyaaa-e minhum wal amwaat. Birahmateka ya Arhamar Rahemeen.
Prophet said
“….on the Resurrection Day God will increase honour of one who pardons an oppressor, seeking thereby the pleasure of God..” – H: Tirmizi. N: Abu Kabsha ‘Aamiri.
“A mischief monger (causing discord) shall not enter paradise.” -- H: Bukhari and Muslim. N: Huzaifah.