11 In him we have obtained an inheritance, having been predestined according to the purpose of him who works all things according to the counsel of his will, 12 so that we who were the first to hope in Christ might be to the praise of his glory. 13 In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, 14 who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory.
Paul is speaking to the Jews in Ephesus. And, although their concept of the coming Messiah sustained them before the God-man came to earth, God planned from the beginning that the Jews would also become heirs with Christ. As a converted Jew, Paul’s concern for his fellow Jews was uppermost in his mind—that they also would believe and be “sealed with the promised Holy Spirit.”
For me, being sealed by the Holy Spirit means I am protected from harm, comforted in troubled times, and I live with the knowledge that God knows what’s best for me.