"I desire that the Feast of Mercy be a refuge and shelter for all souls, and especially for poor sinners. On that day the very depths of My tender mercy are open. I pour out a whole ocean of graces upon those souls who approach the Fount of My Mercy. The soul that will go to Confession and receive Holy Communion shall obtain complete forgiveness of sins and punishment. On that day all the divine floodgates through which graces flow are opened. Let no soul fear to draw near to Me, even though its sins be as scarlet (699)."

There it is: Jesus promises that the soul that’s been to Confession and receives Holy Communion will be completely wiped away of the two stains that are on our soul. Those stains are sin and the punishment due to sin. The special grace promised by our Lord for Divine Mercy Sunday is nothing less than the equivalent of a complete renewal of baptismal grace in the soul.

But how can you receive this complete forgiveness of sins and remission of all punishment? After all, churches are closed and Confession and Communion are not available. 

There is, however, still a way to receive this grace.

Do these three things on Divine Mercy Sunday with the intention to turn away from sin in your life:

Since you are unable to get to Confession, make an Act of Perfect Contrition, instead. As the Catechism of the Catholic Church states, “Among the penitent's acts contrition occupies first place. Contrition is 'sorrow of the soul and detestation for the sin committed, together with the resolution not to sin again'" (1451).

You thereby will be completely forgiven of all sins, even “mortal sins if it includes the firm resolution to have recourse to sacramental confession as soon as possible” (Catechism, 1452). 

How to Make an Act of Perfect Contrition 
Click Here

Since churches are closed and you cannot receive Holy Communion, make a Spiritual Communion instead, asking God to come into your heart as if you received Him sacramentally — Body, Blood, Soul, and Divinity. For instance, you can say this:

Act of Spiritual Communion

My Jesus, I believe that You are present in the Blessed Sacrament. 
I love You above all things and I desire You in my soul. 
Since I cannot now receive You sacramentally, 
come at least spiritually into my heart. 
As though You were already there, 
I embrace You and unite myself to You; 
permit not that I should ever be separated from You. 
Amen. 
Again, do this act of trust with the intent to return to the sacrament of Holy Communion as soon as possible.  

Lord Jesus Christ, You promised St. Faustina that the soul that has been to Confession [I’m unable, but I made an Act of Contrition] and the soul that receives Holy Communion [I’m unable, but I made a Spiritual Communion] will receive the complete forgiveness of all sins and punishment. Please, Lord Jesus Christ, give me this grace.