The blood covenant is with the Father and the Son. We are joined to the Son by the Holy Spirit when we received the truth of the gospel.
When we hear the word of Christ - we believe and then we are sealed by the Holy Spirit.
Ephesians 1:13 (NASB)
[SUP]13 [/SUP] In Him, you also, after listening to the message of truth, the gospel of your salvation—having also believed, you were sealed in Him with the Holy Spirit of promise,
We can grieve the Holy Spirit by not speaking words of grace, having malice, bitterness, anger, wrath..etc. But we are still sealed by Him.
Ephesians 4:29-31 (NASB)
[SUP]29 [/SUP] Let no unwholesome word proceed from your mouth, but only such a word as is good for edification according to the need of the moment, so that it will give grace to those who hear.
[SUP]30 [/SUP] Do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption.
[SUP]31 [/SUP] Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice.
Some say that we can as an act of our will walk away from Christ. I don't believe that. There may be people that are sick in their minds and in their thinking and do stupid things.
Can I with an act of my will un-born myself from being a human being? I believe we cannot do the same thing as we are born again and we are in Christ now and sealed with the Holy Spirit. We can't "un-born" ourselves from Christ. Sin cannot separate us from Christ as He took away all sin. It's unbelief in Christ that is the only sin that the Holy Spirit convicts the world of.
Another thing that happens is that people read scriptures to do with salvation in this earth while we are living here and equate that to not going to heaven if we fail to experience the life that is ours in Christ.