To receive these graces, the only condition is to receive Holy Communion worthily on Divine Mercy Sunday (or the Vigil celebration) by making a good confession beforehand and staying in the state of grace and trusting in His Divine Mercy.
By these conditions, our Lord is emphasizing the value of confession and Holy Communion as miracles of mercy. The Eucharist is Jesus, Himself, the Living God, longing to pour Himself as Mercy into our hearts. In addition, our Lord says through St. Faustina that we are to perform acts of mercy:
“Yes, the first Sunday after Easter is the Feast of Mercy, but there must also be acts of mercy” (742).
“The graces of My mercy are drawn by means of one vessel only, and that is trust. The more a soul trusts, the more it will receive” (1578).
The worthy reception of the Eucharist on Divine Mercy Sunday is sufficient to obtain the extraordinary graces promised by Jesus.