One time I asked a spiritual director where God was when I would fall into sin. He looked at me like I had missed some basic point along the way.
"He's suffering with you on the cross."
Sanctity is our vocation, because our happiness and beatitude consists in imitating the holiness of the Creator from Whom we have come and in Whom we live and move and have our being. But if we imagine (in a spiritually reduced and binary way) that God is with us in the joy of holiness and not with us in the misery of sin, we have missed the point of Christianity.
The good news of our faith is precisely that God has entered into the misery and unhappiness we have brought upon ourselves with our sins in order to blaze a trail out of it for humanity. That trail is called the Resurrection of Jesus Christ.
So in a state of sin we feel unhappy because we have touched, to some degree, the alienation from God that is the final and complete human suffering. But for us who have been baptized into the death and Resurrection of Christ, our liberation is the knowledge that this is just that, a feeling that does not accurately reflect our spiritual condition. For God in Christ has joined us in the suffering of our miserable alienation, and this knowledge is the faith that saves precisely because it reveals the path that Christ has walked from the death of sin to the new life of the Resurrection.
This is not to say that there is no such thing as the final impenitence that leads to hell or the possibility of truly unrepentant mortal sin that cuts off the soul from grace, but only to say that the basic question of the spiritual life is not whether to be good or bad, to be a sinner or a saint (that is, in the way the world thinks of saints.) The basic question of the spiritual life is to ask ourselves what sort of sinner we want to be. We can follow the wisdom of this world and become the sort of sinner who lets his sin make him ever more bitter and selfish, or let the tragedy of sin in our lives and the world break our hearts open into humility for ourselves and compassion for others.
That's how suffering and alienation come to be transformed into kindness and communion, and that's what the death and Resurrection looks like when its Mystery comes to make a home in our hearts.