Confession: What If I remembered another sin after confession?

I was asked this question:

"What if I had a good confession, confessed all my sins and then later realized that I forgot a particular sin, wasn't I forgiven for all my sins. Do I need to confess the sin that I just remembered?"

My understanding is that when you go to confession you are to identify all you mortal sins (and it is a good idea to confess venial sins that are troubling and chronic) and confess them with true contrition.

At the end of confessing we say "please forgive me for all these sins and for any sin that I have committed but cannot recall.

We are then forgiven for our sins spoken and for those that we have committed but cannot remember.

However, if at a later time we recall a mortal sin that we had committed, I believe that we are to confess it right away, bringing it out into the light, speaking it, and receiving absolution.

Many of us repress things in order to not deal with them, as long as they are repressed, we cannot grow from them. If God allows them to surface at a later time, just forgetting them, or telling oneself that I was already forgiven, robs us of the graces and benefit associated with contemplating our sin during preparation for confession, speaking the sin out loud, and discussing it with the priest, and then hearing the words and receiving absolution.

The more we confess the sin we receive additional graces to avoid repeating it again.

The idea that you are forgiven for all sins is associated with everything that you disclosed and for everything else that you have committed but are unaware of.....

If at a later time you realize that you have fallen, mortally, it should be confessed.