The problem with humankind as a party in covenant with God is that we are neither trustworthy nor dependable. That is why God cut the covenant with His own Son. We are in no position to keep our end of any kind of agreement.— It Is Finished, page 112
This is the thesis of the book of Hebrews; Christ is the mediator of the new covenant. He is our surety. And he is the one who is able to fulfill the terms. You and I are the beneficiaries of his sufficiency. Praise God!