The Divine Mercy devotion is given to us by Christ for these days. It is important that we listen to Him.
Do not listen to those who preach a Gospel of false compassion and mercy. This is a very dangerous teaching which will mislead and lead to final death. To make allowances for sinful behaviour is not the Way of the Lord. Jesus calls us to conversion and to a holy life and the Saints are witnesses to the True Love and Mercy that Jesus gives. You cannot experience Gods Mercy unless you turn away from sin. To tell those who are living in sin that God loves them as they are is false and dangerous. Jesus hates sin and we only need to look at the Sufferings He endured for our sake to know this. For anyone to say that sin is okay is speaking on behalf of the evil one who wants to destroy our souls.
Listen to Christ and to the Church's teaching and to the Voices of the Witnesses over the centuries. Do not be deceived. We are living in a time of great grace but it is up to each of us to Choose Christ or the voices of the anti Gospel or anti Christ. We may be asked to give our lives for Christ and for that we must be prepared at all times.