The Word of God says, "God is Spirit and those who worship Him must worship in spirit and Truth" (Jn 4:24). To worship in spirit (or in Spirit) is to worship with your heart or human spirit (or to worship according to the Holy Spirit). This is opposed to worshipping in the flesh and according to the senses, as in the Old Testament. And you have to worship in Truth. To worship in Truth is to worship according to the Word of God. When you live in sin and say that you are praising and worshiping God, you are foolish: God has millions (or billions) of angels who worship and praise Him; and there are millions (or billions) of human beings who worship and praise God. If you live in disobedience to the Word of God that you know, even if you sing songs, and worship five hours everyday, you will still end in Hell Fire, unless you repent of your sin(s). Worship in spirit and Truth!