When David sinned, he pleaded in prayer (Psalm 51) saying, “Take not your Spirit from me.” Must have been a real possibility. Jesus, in the parable of the sower, talks of grain that is planted, germinates and grows for a time, then dies in the heat of the sun. Seems dangerous to assume that what He gives, He can’t reclaim.
Good catch! Glad you brought it up. The difference is that with the new covenant, God DOES put His Spirit within us and He stays there because he is the "earnest of our inheritance". It means He is the "down payment" until the time when we take possession of our eternal home in Heaven. Like Jesus said in John 14:16, "And I will pray the Father, and he shall give you another Comforter, that he may abide with you for ever". Even the Prophets of God in the Old Testament times had the experience of the Holy Spirit coming and going from them, but now the Holy Spirit is WITHIN us and He does not leave us.
God promises to Israel included this:
And I will give them one heart, and I will put a new spirit within you; and I will take the stony heart out of their flesh, and will give them an heart of flesh: That they may walk in my statutes, and keep mine ordinances, and do them: and they shall be my people, and I will be their God. (Ezekial 11:19,20)
And again in:
A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh. And I will put my spirit within you, and cause you to walk in my statutes, and ye shall keep my judgments, and do them. (Ezekial 36:26,27)