Committed in Blood

In requiring blood to validate the New Covenant, God is saying that even if it takes the last drop of His blood to keep the covenant then He will provide it. This is how committed God is to blessing you. This is how faithful God is to keep His word of blessing for you, to make you His son and to be available to walk with you in a loving helpful way all the time. The initiative is not on our part to keep the covenant but God says that it is on His part.
"But Zion said, 'The LORD has forsaken me, And the Lord has forgotten me.' 'Can a woman forget her nursing child And have no compassion on the son of her womb? Even these may forget, but I will not forget you. 'Behold, I have inscribed you on the palms of My hands; Your walls are continually before Me.'" (Isaiah 49:14-16 NASB)
Many times we think that God has forsaken us. Here the Lord says that even as a woman remembers her children and even they may forget them, the Lord will not forget His covenant children. A part of the covenant was to make a scar on the hand and sometimes to rub gunpower into it to make the scar pronounced so the bearer would not easily forget his commitment.
Here the Lord says that He has inscribed us upon the palms of His hands. This was not a scar but the wounds of the cross where the Roman soldiers drove the nails into Jesus' hand. These wounds will for eternity be in the palms of Jesus to remind us of His love for us. The wounds are not so much to remind the Lord, because He never forgets, but it is to assure us of His continual love for us.
The last part says that our walls are continually before Him. That is He is continually watching out for our protection and keeping us safe. A part of our covenant with Him is His guarding us against our enemies. Jesus taught His disciples to pray, "...and lead us not into temptation but deliver us from evil...." Matthew 6:13
Faithful is He who promised who will also perform it.