Hi, Elect.
The answer to your question truly is found in the very next verse, BUT NOT IN THE MANNER IN WHICH SOME PEOPLE HERE HAVE ERRONEOUSLY STATED. We read:
"In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory." (Ephesians 1:13-14)
The key to understanding what we just read is found in understanding exactly what "the earnest" is. Before explaining the same, here are some similar verses to consider:
"Now he which stablisheth us with you in Christ, and hath anointed us, is God; Who hath also sealed us, and given the earnest of the Spirit in our hearts." (II Corinthians 1:21-22)
Again:
"For we that are in this tabernacle do groan, being burdened: not for that we would be unclothed, but clothed upon, that mortality might be swallowed up of life. Now he that hath wrought us for the selfsame thing is God, who also hath given unto us the earnest of the Spirit." (II Corinthians 5:4-5)
Unlike many today, the Apostle Paul knew EXACTLY what he was talking about or referring to when he spoke of "the earnest". You see, "the earnest" has to do with "earnest money" or with a downpayment which a potential buyer would make to show that he/she was "earnestly" considering finishing the transaction AT SOME LATER POINT IN TIME. In relation to the same, we read:
http://www.realestateabc.com/insights/deposit.htm
IOW, seeing how God "earnestly" desires to purchase us, He has given us "the earnest" or the downpayment "of the Spirit" in hope that He will eventually "SEAL the deal" AT SOME LATER POINT IN TIME. IOW, the purchasing process has not yet been completed. Can God ever get His "earnest" back? You'd better believe that He can. In fact, TWICE, IN JUST THE LAST 4 YEARS, my wife and I have received our "earnest payments" back on two different houses which we were "earnestly" considering buying. On one occasion, mold was found in the home upon inspection and we received back 100% of our "earnest money". On the other occasion, the man who was selling the house which we had made a downpayment on, thereby giving him our "earnest money", didn't have legal right to be selling the house and, again, we received back 100% of our "earnest money" deposit or downpayment.
Again, here is what the word "earnest" means as used by the Apostle Paul:
Greek Lexicon :: G728 (KJV)
Anyhow, the point is that if God finds something wrong with that which He "earnestly" desires to purchase BEFORE THE FINAL TRANSACTION IS COMPLETE, then He, too, can get back His "earnest of the Spirit" AND THE DESIRED PURCHASE WILL NEVER BE COMPLETED.
Hopefully, this helps.