Keep count of your istighfār — the Prophet ﷺ sought Allah's forgiveness more than seventy times in a single day.
Istighfār is not only for those conscious of a particular sin. The Prophet ﷺ — whose past and future faults were already forgiven — said: “By Allah, I seek Allah's forgiveness and repent to Him more than seventy times a day.” (Ṣaḥīḥ al-Bukhārī 6307) In another narration he said: “O people, repent to Allah, for I repent to Him a hundred times a day.” (Ṣaḥīḥ Muslim 2702) It is a habit of the heart, not a last resort.
Ibn ʿAbbās reported the Prophet ﷺ said: “Whoever persists in seeking forgiveness, Allah will grant him relief from every worry, a way out of every hardship, and provide for him from where he does not expect.” (Abū Dāwūd 1518) The Qur'an makes the same connection in the words of Nūḥ عليه السلام: “Seek forgiveness of your Lord — He is ever Forgiving. He will send rain upon you in abundance, and give you increase in wealth and children.” (Nūḥ 71:10–12)
No fixed number is obligatory. The counter above is set to 100, following the narration of a hundred times a day. Many keep it on the tongue while walking, driving, or working — istighfār needs no wuḍūʾ, no direction, and no particular time. It is also part of the adhkār said after every fard prayer, where the Prophet ﷺ would seek forgiveness three times on finishing.