First of all, we shouldn't be hopeless of acceptance of our repentance. Just reflect on His divine mercy. He is All-Merciful. On the other side, we can't be overwhelmed by just saying Astagfirullah and think that the repentance has been accepted. The biggest sign of the acceptance of Tawbah is that we never turn back to that particular sin. If we have reached that level, it means that tawbah has been accepted. Normally, we all should have hope and fear in regards to our deeds and this factor would balance our spiritual life. Forgiveness, in general, by itself is a way to seek proximity to Allah swt and it is recommended especially on Thursday nights.
By the way, mystics say that committing sins need a life long repentance as that person has crossed the boundaries and limits set by Allah swt. So whenever a person remembers his shameful act, he should repent for the things which he has committed in past.