By His nature, God is merciful and forgiving for repentant sinners. We can find relevant passages in Old Testament: "The Lord is patient and full of mercy, taking away iniquity and wickedness, and leaving no man clear" (Numbers 14:18); "The Lord is gracious and merciful: patient and plenteous in mercy. The Lord is sweet to all: and his tender mercies are over all his works" (Ps 144:8); "The blessing of God maketh haste to reward the just, and in a swift hour his blessing beareth fruit". (Ecclesiasticus 11:24); "He will turn again, and have mercy on us: he will put away our iniquities: and he will cast all our sins into the bottom of the sea" (Micheas 7:19).
New Testament contains also passages telling us about God's merciful love for weak, repentant sinners: "For God sent not his Son into the world, to judge the world, but that the world may be saved by him" (John 3:17); "For the Son of man is come to seek and to save that which was lost" (Luke 19:10); " The Lord delayeth not his promise, as some imagine, but dealeth patiently for your sake, not willing that any should perish, but that all should return to penance" (2Peter 3:9)
St Romuald even said that as much as eighty percent of the Holy Scripture praise the mercy of God who is not only just but also full of mercy. The more sins, passions, weaknesses we have the more trust we should have in God's understanding and mercy. It is more pleasing to Him than doubting and distrusting soul: "But let him that glorieth glory in this, that he understandeth and knoweth me, for I am the Lord that exercise mercy, and judgment, and justice in the earth" (Jermias 9:24)