Paul, on his 2nd missionary journey, redirects himself hearing the call to Macedonia and now is in Rome. As the church ministers to his needs, Paul tells them to "work our with fear your own salvation." Note up front he is not talking about our justification but our sanctification. Paul puts his finger on the entirety of the life of the child of God!
This cannot mean that we are to work our salvation as it is the gift of God by grace. Not of works and we as we are the workmanship of God. This work of salvation has already been FINISHED....once offered on the cross. Now we can understand what Paul means. Christ works it (of God alone a gift) and we are to work OUT the salvation that has been given to us (OUR responsibility.) This is a process in our lives that affect ALL of our living. It MUST be worked out in our lives. We are not still like pictures, furniture, vases but Christians who have received HIS Spirit and we stand in the calling to work our this salvation. His glory MUST show itself in and through us!
We have the Spirit in our hearts and are living members of Christ who gives us His word to continually exercise ourselves in these Christian virtues. God did not save us just so we can bask in our salvation, but it is about GOD and unto HIM and we are called to work out this salvation that GOD'S pleasure, purpose, and HIS glory may be shown and done! God's glory first and foremost in ALL our life! If it is not, we definitely must stop and reevaluate the path we are on. We are to do that with fear and trembling. A tremendous calling to be Christians and to be to the glory of the Almighty God instead of our own desires and pleasures. We fear and tremble when we see the tremendous calling that is ours to show God's glory in our lives ALWAYS! Often times we must pray for this in our lives and we may not at any time in our lives let the glory of God go! What a challenge and difficult calling!
We must steep ourselves in the Word of God as we know our responsibilities and to exercise ourselves and our calling in the to His glory! (Q&A 82, Cannons of Dort 3&4 heads.) God's pleasure in us. He works the willing and the doing. God with the Holy Spirit presses this upon us and even as He calls us He WILL also qualify us and give us the grace to one end......HIS GOOD PLEASURE.