“His divine power has given us everything we need for a godly life through our knowledge of him… For this very reason, make every effort to add to your faith goodness; and to goodness, knowledge;” (II Peter 1:3,5 NIV)
Nobody can be good by their own power. But those of us who are true believers are given divine power to live godly lives. Therefore, since we have this power, we should make every effort to use it by doing good. We have no excuse for not doing good.