1 Pet 2:10: Once you were not a people [at all], but now you are God’s people; once you had not received mercy, but now you have received mercy.

2 Cor 4:1: Therefore, since we have this ministry, just as we received mercy [from God, granting us salvation, opportunities, and blessings], we do not get discouraged nor lose our motivation.

My declaration would be:

I am now God’s child and I have received mercy from the Lord. I walk with a conscious awareness of the mercy of God over my life.

1 Cor 6:11 AMP/AMPC:

And such were some of you [before you believed]. But you were washed [by the atoning sacrifice of Christ], you were sanctified [set apart for God, and made holy], you were justified [declared free of guilt] in the name of the Lord Jesus Christ and in the [Holy] Spirit of our God [the source of the believer’s new life and changed behavior].