2:38 Then Peter said to them, “Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit. 39 For the promise is to you and to your children, and to all who are afar off, as many as the Lord our God will call.”
What is a gift? The Cambridge dictionary defines a gift as "something that is given". Gifts are not earned, bought, or acquired by the one who receives it. When a person chooses Jesus they also get a Gift. That Gift is His Spirit. It is the very Person and Presence of Jesus inhabiting our minds and transforming our very thoughts and motives. The results of this Gift are love, joy, peace, long suffering, gentleness, kindness, and self control.
Note that His Spirit is called both a Gift and a Promise. The changes He brings are not instantaneous. It is not a rewriting of the hard drive of our brain. His work, His influence, is not forced on us. We still have the freedom to resist. God is a Gentlemen. No changes are made without our permission. No journeys are taken without our consent. No knew thought patterns are implanted without our cooperation. God is not into brainwashing. Love never manipulates or forces. Love respects freedom above all else. This is why in the Revelation Jesus is portrayed as standing at the door and knocking, gaining entrance only if we choose to let Him. On the flip side Satan forces everyone by whatever means he can. Lying, manipulation, cohersion, man made laws, etc...
The Gift is His presence. The Promise is His mind and heart, His very character infusing the ever unique personality He gave us from the start.
Is life with His presence different? Ask Samson. Ask King David who begged that God's Spirit not be taken from him after his moral collapse. Ask the disciples. When James and John met Jesus they were known as the sons of thunder. Their fuse was short and their anger long. After a Samaritan disrespected Jesus one day, John asked if He could call down fire from heaven and burn up the entire village. ISIS anyone?
That same John became know as the beloved disciple and his writings are like no one else's. He is a witness of the power and influence of His Spirit.
The Gift. The Promise. Don't leave home without Him.