You're mixing up the religion of Judaism with biblical commandments of Jesus Christ. When you reject biblical holy days, you are rejecting the instructions of Christ himself to his followers.
You fail to recognize that Christ lived under the old covenant, and that we now live under a new covenant.
Galatians 4:9-11
But now, after that ye have known God, or rather are known of God, how turn ye again to the weak and beggarly elements, whereunto ye desire again to be in bondage?
Ye observe days, and months, and times, and years.
I am afraid of you, lest I have bestowed upon you labour in vain.
Or, if you'd rather...
Galatians 4:21-26
Tell me, ye that desire to be under the law, do ye not hear the law? For it is written, that Abraham had two sons, the one by a bondmaid, the other by a freewoman.
But he who was of the bondwoman was born after the flesh; but he of the freewoman was by promise.
Which things are an allegory: for these are the two covenants; the one from the mount Sinai, which gendereth to bondage, which is Agar. For this Agar is mount Sinai in Arabia, and answereth to Jerusalem which now is, and is in bondage with her children.
But Jerusalem which is above is free, which is the mother of us all.
Christ did not give us a Spirit of bondage (to days, and months, and times, and years), but a Spirit of freedom.