Christ as the Binding Agent.

God, by His nature is Holy. We are not. If it was just God and "us" it would be like oil and water. There would be no cohesion.
Christ was fully God and Christ was fully human. The God nature in Christ binds with God's Holy nature and the human nature in Christ binds with our human nature.
This is why Christ is between us and God. He is our "binding agent" because it is through Him that entities with two opposing natures can be united into a cohesive whole.
gently,laura