So, what is joy "inexpressible"?It is joy in the face of sadness, joy you cannot quantify or sometimes even justify. You are at peace and content in the face of situations and days that are not fair, not ordered, not deserved nor expected and certainly not planned.
You can say with the hymn writer "it is well with my soul" because "when sorrows like sea billows roll" you are at peace with God.
Lord God, Let me learn my lessons, be found obedient, repent when I must, forgive where I should but let me always say "it is well with my soul". Amen.
My covenant was with him of life and peace; and I gave them to him for the fear wherewith he feared me, and was afraid before My Name.