"This is highly necessary if we are to live truly godly lives. You see, this is the situation: By nature we are so unfruitful in good works and so dead in ourselves that we lack any ability to bring forth something good. We are like the holy woman, Sarah, Abraham's wife, who was unable to conceive seed because she was barren by nature. Her womb was also dead because of her old age (Rom. 4:19). After Sarah received the promise that she would deliver a son in her old age, she mixed this promise with faith and received strength to conceive seed "because she judged him faithful who had promised" (Heb.11:11). We poor, depraved, and barren people are in the same situation. In ourselves we are not able to produce even one good thought, but we become able to do so because God has promised power and ability to live a godly life and good works to all who are joined to him with their whole heart. Only those who, like Sarah, mix these promises with faith will receive the power to bring forth good works for the glory of God and to live truly godly lives.
This is a great mystery of the kingdom of grace, of which worldly people are complete ignorant. That is why, when they occasionally have the desire to lead a godly life, they begin in their own strength, without faith and without earnestly looking at the promised help of the Lord our God, who is our strength (Joel 3:16). Because their own strength is useless to bring forth the power of true godliness, they soon tire of it and stop altogether. Or they only attain a form of godliness that satisfies them. This happens because they do not think it necessary to receive God's help to love a godly life. The crafty ways of our spiritual enemy keep their need for this hidden from them." pg. 158,159 Willem Teellinck 'The Path Of True Godliness'