Grace and peace are two essential elements for the Lord to accomplish what He wants with us on this earth. It was by grace that Paul was so abundantly able to labor more than all the other apostles (I Cor. 15:10). In II Cor. 1:12 he testified that his daily life was conducted according to this grace. Later on in chapter 12 of the same letter, he spoke of how the Lord impressed upon him that this grace is sufficient to live above anything that might seem like a thorn in the flesh. No doubt, it was just such an experience of grace that produced a situation of Paul and Silas "praying and singing hymns of praise to God", in the most miserable of human conditions imaginable, as recorded in Acts chapter 16.

I think it was in a message by Ray Stedman I read that grace is God being everything to us in the person of our Lord Jesus Christ. Only when we enter into the realization and enjoyment of God as our source of supply for every detail of our daily living, in Christ Jesus, will we experience him as our peace. The peace is the opposite of what we experience when we choose to take things into our own hand and live by our carnal mind. That is why Paul opened and closed all his letters with "grace and peace". We need grace and peace to hear the message of Christ in us as our life. Once we have heard it, we need grace and peace to live it.