God is jealous. He saved you from serving the devil to be His very own bride. He expects total adoration and perfect obedience. Religious holy days are one of the devil’s and world’s favorite ways to seduce you into spiritual adultery, where you will ignorantly make love with pagan idolatry and the devil, often in the name of Christianity. When God sees this adultery, He turns to be your enemy (Jas 4:4).
God is jealous. He knew religious customs of other nations were attractive, so He warned His people strictly to reject all of them. He would not accept any pagan religious traditions, even if done to Him (Deut 12:1-4,29-31). He demands perfect obedience, without turning to the right or the left, without adding or taking away (Deut 5:32; 12:32). He expects you to come out and be separate (II Cor 6:14-18).