What made the betrayal of Judas irreversible for his soul was that he despaired and committed suicide, rather than repenting.
The reaction of Judas is contrasted with the reaction of St. Peter to the realization of his denial -- he repented and wept bitterly.
There at the Passion we see all of mankind, and all of the ways that we can be toward God for good or ill. Judas with his betrayal and overt treachery, St. Peter with his open denial of Christ, St. John who stayed with Christ until the end at the foot of the Cross, and the rest of the disciples, who simply all ran away and forsook Christ. There are times when we resemble each of these.
We identify with Judas at those times in the service, and then we understand the depths of our need to repent, and we understand just how paltry and superficial our attempts at true repentance really are. But we are not left in despair, but rather with the realization that God in his mercy has given us a way out after we have sinned -- the same way that was available to Judas, but that he did not take.
And of course, throughout Holy Week, and especially at Pascha, we have the women, who were the most faithful of all. Generations of babushkas and yiayia's under the worst of situations in the history of the Church have only reinforced that.
We are not meant to identify only with Judas, or only with St. Peter, etc... During Holy Week we go through the entire gamut of human experience. And it culminates in the exuberant, bursting joy of Pascha, which leaves one feeling like one is walking on air for a week.
We have a retired Episcopalian priest who recently became Orthodox, and who last year went through his first Lent, Holy Week, and Pascha, and he declared it to be the most life-changing thing he had ever experienced. It most certainly is. And the nice thing about it is that about the time our hearts start to harden and cool a little, a year has passed, and the Church leads us through the path to repentance and joy once again...
I would say that even bringing us to a point of repentance is a gift from God. Please consider some of the scriptures on repentance:
"...if perhaps God may grant them repentance leading to the knowledge of the truth," 2 Tim 2:25