Grace - GOD's enabling power released to effectively execute what God has called us to do despite adverse conditions.

And he said unto me, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me. (2 Corinthians 12:9) http://dailybible.co/120.kjv.

Jesus command to us to rejoice and be exceedingly glad when we are reviled, persecuted, and lied on - Matthew 5:11-12. This cannot be done if we are nurturing and mindful of the flesh (Romans 8:5-8). But when we are born-again, Holy Spirit-filled believers, we have an inner joy in the Holy Spirit that gives us an inner peace and approval from God that we are pleasing Him (Romans 8:16-17; 14:17-19). This strength comes the Spirit of Christ - the Holy Spirit. This is the work of grace! The work/power of Holy Spirit! His grace... His strength... Is perfect! More than sufficient to keep us and present us faultless before GOD's throne - Jude 1:24-25; Colossians 1:19-29). Grace is not excuse for sin! - (Romans 6:1-23). Grace is the power (the Holy Spirit - nature and character of God) given to end sin and put us in right relationship with God. And the Holy Spirit (which is the Spirit\Life of God) is more than sufficient for us to live the Christ Life... The Life of the Kingdom!

Paul, the apostle of Jesus Christ, like many of us true believers struggled with suffering for righteousness. It is more tolerable and logical to suffer when we sin against God, but when we are pleasing him we expect God to cushion the blows the enemy strikes at us. Paul found out, like many of us, it is not always so. Sometimes God allows them that we do not forget or become prideful and think too highly of ourselves as ministers of Christ. Our humility in service, therefore qualifies us to receive more grace (James 4:6) and approval from the Lord (Matthew 23:12; Luke 1:52) and prove that we are truly offspring of God who is humble (Philippians 2:5-11). It should be noted that Paul is not referring to "sin" as his "infirmities/weakness"! Those who are weak to sin are carnal minded and cannot please God (Romans 8:7-9). Many false believers use this verse to justify their carnal/sinful lifestyle and even use it to testify that the more God forgives them, the more they bring glorify God. Paul says such self-proclaimed believers have a perverted view of the gospel and "their condemnation (by God) is just" - (Romans 3:5-8). Paul made it clear that "the thorn in his flesh" was an angel of Satan sent to buffet - harass, disturb and torment - him during his ministry (2 Corinthians 12:7) and this he listed in the previous chapter (2 Corinthians 11:22-33) as he defended his ministry against false apostles and carnal believers who thought that his suffering was proof that he was not called to the ministry. But Paul said he would boast in his sufferings for the sake of Christ and the gospel because his willingness to endure these hardships revealed the power of God to sustain and keep him and gave true glory to the power of God. Peter also confirmed this message (1 Peter 4:12-19).