How saved are you? The importance of Eternal Security.

2Co 1:22  who has placed his seal on us and has given us the Spirit in our hearts as a down payment.

2Co 1:22  Having put his chotam [seal of ownership BERESHIS 38:18; YECHEZKEL 9:4; Ep 1:13; 4:30; Rv 7:4] on us and having given the eravon (pledge) of the Ruach Hakodesh in our levavot. (hearts Ro 8:16; 2C 5:5; Ep 1:14). [BERESHIS 38:18; YECHEZKEL 9:4; CHAGGAI 2:23] 
OJB

Who hath also sealed us - The word used here (from σφραγίζω sphragizō) means to seal up; to close and make fast with a seal, or signet; as, e. g., books, letters, etc. that they may not be read. It is also used in the sense of setting a mark on anything, or a seal, to denote that it is genuine, authentic, confirmed, or approved, as when a deed, compact, or agreement is sealed. it is thus made sure; and is confirmed or established. Hence, it is applied to persons, as denoting that they are approved, as in Rev_7:3; “Hurt not the earth, neither the sea, nor the trees, until we have sealed the servants of our God in their foreheads;” compare Eze_9:4; see the note, Joh_6:27, were it is said of the Saviour, “for him hath God the Father sealed;” compare Joh_3:33. In a similar manner Christians are said to be sealed; to be sealed by the Holy Spirit Eph_1:13; Eph_4:30; that is, the Holy Spirit is given to them to confirm them as belonging to God. He grants them His Spirit. He renews and sanctifies them. He produces in their hearts those feelings, hopes, and desires which are an evidence that they are approved by God; that they are regarded as his adopted children; that their hope is genuine, and that their redemption and salvation are sure - in the same way as a seal makes a will or an agreement sure. God grants to them His Holy Spirit as the certain pledge that they are His, and shall be approved and saved in the last day. In this there is nothing miraculous, or in the nature of direct revelation. It consists of the ordinary operations of the Spirit on the heart, producing repentance, faith, hope, joy, conformity to God, the love of prayer and praise, and the Christian virtues generally; and these things are the evidences that the Holy Spirit has renewed the heart, and that the Christian is sealed for the day of redemption.
And given the earnest of the Spirit - The word used here (ἀῤῥαβών arrabōn from the Hebrew צרבון ‛arabown means properly a pledge given to ratify a contract; a part of the price, or purchase money; a first payment; that which confirms the bargain, and which is regarded as a pledge that all the price will be paid. The word occurs in the Septuagint and Hebrew, in Gen_38:17-18; Gen_38:20. In the New Testament it occurs only in this place, and in 2Co_5:5, and Eph_1:14, in each place in the same connection as applied to the Holy Spirit, and his influences on the heart. It refers to those influences as a pledge of the future glories which await Christians in heaven. In regard to the “earnest,” or the part of a price which was paid in a contract, it may be remarked:
(1) That it was of the same nature as the full price, being regarded as a part of it;
(2) It was regarded as a pledge or assurance that the full price would be paid. So the “earnest of the Spirit,” denotes that God gives to his people the influences of his Spirit: his operation on the heart as a part or pledge that all the blessings of the covenant of redemption shall be given to them.
And it implies:
(1) That the comforts of the Christian here are of the same nature as they will be in heaven. Heaven will consist of like comforts; of love, and peace, and joy, and purity begun here, and simply expanded there to complete and eternal perfection. The joys of heaven differ only in degree, not in kind, from those of the Christian on earth. That which is begun here is perfected there; and the feelings and views which the Christian has here, if expanded and carried out, would constitute heaven.
(2) These comforts, these influences of the Spirit, are a pledge of heaven. They are the security which God gives us that we shall be saved. If we are brought under the renewing influences of the Spirit here; if we are made meek, and humble, and prayerful by his agency; if we are made to partake of the joys which result from pardoned sin; if we are filled with the hope of heaven, it is all produced by the Holy Spirit, and is a pledge, or earnest of our future inheritance; as the first sheaves of a harvest are a pledge of a harvest; or the first payment under a contract a pledge that all will be payed. God thus gives to his people the assurance that they shall be saved; and by this “pledge” makes their title to eternal life sure.

σφραγισαμενος
G4972
V-AMP-NSM
σφραγίζω
to stamp for security

Part of Speech: Verb
Tense: Aorist
Voice: Middle
Mood: Participle
Case: Nominative (subject; predicate nominative)
Number: Singular
Gender: Masculine

δους
G1325
V-2AAP-NSM
δίδωμι
to give

Part of Speech: Verb
Tense: second Aorist....What is the Second Aorist?
Voice: Active
Mood: Participle
Case: Nominative (subject; predicate nominative)
Number: Singular
Gender: Masculine

Eph 1:13  You, too, have heard the word of truth, the gospel of your salvation. When you believed in the Messiah, [Lit. in him] you were sealed with the promised Holy Spirit, 
Eph 1:14  who is the guarantee of our inheritance until God redeems his own possession [Lit. of the possession] for his praise and glory.

Can a genuine believer in Christ Jesus be "unsealed" when sealed by the Spirit?

J.