Paul's ministry was to be God's ministry. God's strength, God's power can only be effective when we understand our own weakness. I think understanding this idea is what has made Alcoholics Anonymous so effective in its Twelve-Step program. It's based on the principle that the alcoholic must recognize individual helplessness and fall back into the arms of the Higher Power. For the recovering alcoholic, there is probably a sense that they have to live under grace every day because the battle of temptation is every day.
Spirituality is for people who have been there.
We have to know weakness to know God's strength. Interestingly, if we look at the history of the Christian church, the saddest chapters are the times when the church has been most powerful, at least powerful in terms of worldly power, when it had control and influence and wealth. The Crusades, the Inquisition, the abuses that led to the Reformation came when the church had a great deal of worldly power. Perhaps the Salem witch trials came about only because the Congregationalists, our ancestors in the faith, had too much worldly power in 17 th century colonial Salem. The church so often has been at its weakest when it has been the most powerful in influence.