One reason that God so delights in extending mercy to us is that it results in His mercy dwelling within us, and revealed by us.
"Be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ's sake hath forgiven you" (Ephesians 4:32).
Forever will not be long enough to fully understand the blessing of God forgiving us, nor to fully express our loving thanksgiving to Him. However, since "it is more blessed to give than to receive," being enabled to forgive others as God has forgiven us is an even greater blessing (Acts 20:35). Our Heavenly Father's intends that "we shall be like Him" in character, disposition, inclination, and thus, in His love for mercy. He alone can reveal such goodness within us, and empower us to walk even as we have received (I John 3:2; Colossians 2:6).
Born again believers are in the process of being "conformed to the image of His Son" (Romans 8:29). A primary feature of such grace is that we are "vessels of mercy" (Romans 9:23). This constitutes us as both the forgiven and as forgivers. We may not always feel the effects of the fact. Our thought patterns may not always flow with the current of mercy. And our actions may not always coincide with the truth that mercy is now our delight because we are the sons and daughters of He who "delighteth in mercy" (Micah 7:18). However, it is always true that this is who we are, and it is always the truest desire of our Christ-inhabited spiritual being (Romans 7:22). "Ye are not in the flesh, but in the spirit, if so be that the Spirit of Christ dwell in you" (Romans 8:9).
Forgiving as God forgives is not of human origin. "Without Me, ye can do nothing" (John 15:5). It is, however, meant to be of human expression. "I can do all things through Christ which strengtheneth me" (Philippians 4:13). We must believe that we are the vessels of mercy God declares us to be, and we must remember that vessels do not contain their content for their own benefit. "Love... seeketh not her own" (I Corinthians 13:5). Mercy received is meant to be mercy distributed. In a fallen world, we shall have much opportunity to walk in the blessing of "freely ye have received, freely give" (Matthew 10:8). It is our delight to do so, and may no contrary thought, emotion, or appearance hinder us from the "more blessed" glory of forgiving as we have been forgiven.
"But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you; that ye may be the children of your Father which is in heaven: for He maketh His sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust."