What is said in a general repentance for forgotten sins?

If one has sins they do not remember, they must repent from them generally with the heart, by abstaining from all sins, whether known or unknown to them, regretting their shortcomings in fulfilling God's rights, and resolving never to return to them. It is good to follow this with seeking forgiveness verbally, and the best form of it is Sayyid al-Istighfar (the master of seeking forgiveness).