For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Bryan Naidoo
Any seal is only guaranteed if the person does not tamper with it. We know many a seal has been tampered with and lost its guarantee.
It is the responsible of all persons concerned not to grieve the seal, when you hear his "voice" do not harden your hearts like the children of Israel, only Joshua and Caleb entered the land of rest.
King Saul lost his position as king because he failed to listen to the King of kings. Total obedience to the word of god and Living a life of repentance will help to maintain our seal.
James Kraft
In the old testament, under law works, a person could loose the spirit through disobedience as Saul did.
Under the new testament of grace, once we have accepted Jesus as our only way of salvation, we are sealed by the holy spirit unto the day of redemption. Ephesians 1:13 That seal can not be broken because it was put their by God Himself. It is the seal of the holy spirit that is our righteousness before God because in our flesh we are not righteous.
Since we have to be perfect to go to heaven, and since none of us are, it is the perfect holy spirit that lives in us that is our righteousness. Romans 4:5 When we accept Jesus as full payment for all our sin, past, present, and future, we are accounted righteous before God by faith alone in His finished work on the cross.
It is the spirit in us that says I will never leave you or forsake you. The question is, have you trusted Him to save you? Do you believe that all your sin has been paid for by Jesus blood sacrifice for all your sin. If you have you have eternal life and can never be lost. John 6:37-40 First John 5:13
Since God can not lie, we know that if we have trusted Him to save us by faith alone, that He will do what He said He will do. He will keep us saved until we are safe in heaven with Him.