Prayer for the conversion of a loved one
Here is a prayer from a manual of prayers published in 1851 that beautifully represents our desires and cries out to God for help.
O divine and adorable Savior, thou who art the way, the truth, and the
life, I beseech thee to have mercy upon N., and bring him [or her] to
the knowledge and love of thy truth. Thou, O Lord, knowest all his
darkness, his weakness, and his doubts: have pity upon him, O
merciful Savior; let the bright beams of thy eternal truth shine upon
his mind; clear away the cloud of error and prejudice from before his
eyes, and may he humbly submit to and embrace with his whole heart
the teaching of thy Church. Oh, let not the soul for whom I pray be
shut out from thy blessed fold! Unite him to thyself in the sacraments
of thy love, and grant that, partaking of the blessings of thy grace in
this life, he may come at last to the possession of those eternal rewards
which thou hast promised to all those who believe in thee and who do
thy will. Hear this my petition, O merciful Jesus, who, with the Father
and the Holy Spirit, livest and reignest ever and ever.