For the grace of God has appeared, bringing salvation to all men, instructing us to deny ungodliness and worldly desires and to live sensibly, righteously and godly in the present age,
This instruction comes toward the end of a chapter outlining the duties and roles of believers. We are to be godly, sensible and righteous in all things because the grace of God has come to bring us salvation and instruct us. That grace of God is Jesus. He came to be our permanent sacrifice so that we could be saved from sin and death. As a result of that salvation, we are to be godly (live like God), righteous (innocent, just, acceptable to God), and sensible (with sound mind, soberly, temperately, discreetly). We are also to deny ungodliness (lack of piety or reverence toward God) and worldly desires (any longing or craving that is of the world and not of God.) We cannot accept have the salvation of God and not accept the instruction of God. Of course we all sin, but if we disregard and ignore His instruction we have rejected Him. He has the key to a good life. This is it. If we do not live the way He instructs us our lives will be chaotic and unfulfilling. This is the guide for a life honoring to God and satisfying to us. Heed His instruction and enjoy His salvation.