Christ has authority over all things and we live under His supreme lordship. "Therefore," we succumb to no other rules. Paul exhorts us to hold fast to Christ alone, even when we feel the pressure to succumb to other demands.
Other Demands (16-18): First of these demands were based on the Mosaic Law (foreshadowing Christ). Paul lists them starting with dietary laws ("food or drink"), and then annual ("festival"), monthly ("new moon") and weekly ("Sabbath") observation of days. Beyond these, there were bizarre pagan practices: "self-abasement" (literally, humility) and "worship of angels" and "visions" (literally, things he has seen) and "[being] inflated without cause." Whatever these were, they were captivating the Colossian believers and they were competing against Christ's authority over their lives.
Hold Fast to Christ (19): Saints are devoted to Christ alone. He is our head and we are His body, and we hold fast to Him. And when each member of the body faithfully abides in Christ, the church exhibits the growth that God Himself gives ("growth which is from God"). What would stunt this growth are those who hold fast to other things. But if each member stays devoted to Christ to honor, love and imitate Him, the church most assuredly grows!
 Main verbs in 2:16 and 18 are imperfective imperatives in Greek. They were ongoing issues that had to stop.
 The author of Hebrews also uses the same term (ski-a [σκιά]) for the Levitical sacrifice system (Heb. 10:1).
 The Jews observed drink laws for the general public not found in the OT (cf. Heb. 9:10; Rom. 14:17, 21).
 The Mosaic law issued requirements for each Sabbath day and new moon day (Num. 28:9-10, 11) and annual feasts (Ex. 23:14-17). But since the Law was "only a shadow of the good things to come" and a tutor that pointed us to Christ, the new covenant saint has no obligation to it (Heb. 8:13; Gal. 3:19, 23-25).
 There is uncertainty as to the meaning/referent of nearly every word/phrase in this verse. Many of them occur only here in the entire NT. But the main point of the passage is easy to see: Christ reigns supreme over all other authorities, and we live as joyful and affectionate subjects of our beloved and benevolent King.