Christ died on the Cross and man was bought into “Communion” with Christ, death was defeated by love, per Sacred Scripture, St Paul. Crucifixes appeared since the pagan Roman Empire then after Constantine in religious art etc. The Crucifix is an icon of the invisible God and a window to see the invisible and a everlasting reminder of the Blood spilled for your soul.
This is exactly what the Apostles and Saints of the Church have done and from the start, and many through severe persecution of their belief and worship. They bear witness to the spiritual reality of the Lord and place this in proper context
Your guilt is a result of your transgression which you see much clearer as you walk closer to the Light of the World. And the closer you walk the clearer this becomes. The Sacraments are a gift of the Living God, reconciliation/Communion aid the soul in remaining in a State of Grace with the Lord.
Catholics follow the law of Lex orandi, lex credendi,
“Lex orandi, lex credendi (Latin loosely translatable as “the law of prayer is the law of belief”) refers to the relationship between worship and belief, and is an ancient Christian principle which provided a measure for developing the ancient Christian creeds, the canon of scripture and other doctrinal matters based on the prayer texts of the Church, that is, the Church’s liturgy. In the Early Church there was liturgical tradition before there was a common creed and before there was an officially sanctioned biblical canon. These liturgical traditions provided the theological framework for establishing the creeds and canon.” Wiki Pedia
The Sacrament of Penance and Reconciliation is one of seven sacraments of the Catholic Church.
In asking if Catholics continue to pray in penance aside from the sacrament, while this is true, I doubt they see this as penance as I don’t speaking for myself. I see this as a continuity of on-going conversation with the Lord which develops and grows in time, in other words as an individual you travel from kind of knowing who Christ is, to becoming friends with the Lord, to a deeply rooted friendship in bond and ultimately to love thus a relationship and path. Though as you enter into this way of life at first one may see this as penance, but this is indicative of how one is living in relation to the physical world. Thus its a changing reality and state of mind. This is why on the other end of the spectrum you see and feel an overwhelming state of peace and tranquility. This is where people encounter each other in harmony. For that indeed is the Lords will.
The Cross is most significant, its not that your not seeing it, its that you are seeing it.