Here's the scripture that made me realize that what I celebrate or do not celebrate is nobody else's business:Romans 14:1-13 (note vs 5, 10, 12 - I also wanted to include the context here)
Now accept the one who is weak in faith, but not for the purpose of passing judgment on his opinions.
2 One person has faith that he may eat all things, but he who is weak eats vegetables only.
3 The one who eats is not to regard with contempt the one who does not eat, and the one who does not eat is not to judge the one who eats, for God has accepted him.
4 Who are you to judge the servant of another? To his own master he stands or falls; and he will stand, for the Lord is able to make him stand.
5One person regards one day above another, another regards every day alike. Each person must be fully convinced in his own mind.
6He who observes the day, observes it for the Lord, and he who eats, does so for the Lord, for he gives thanks to God; and he who eats not, for the Lord he does not eat, and gives thanks to God.
7 For not one of us lives for himself, and not one of us dies for himself ;
8 For if we live, we live for the Lord, or if we die, we die for the Lord; therefore whether we live or die, we are the Lord's.
9 For this end Christ died and lived again, that He might be Lord both of the dead and of the living.
10But you, why do you judge your brother? Or you again, why do you regard your brother with contempt? For we will all stand before the judgment seat of God.
11 For it is written, "As I live, says the Lord, every knee shall bow to Me, and every tongue shall give praise to God."
12So then each one of us will give an account of himself to God.13Therefore let us not judge one another anymore, but rather determine this -- not to put an obstacle or a stumbling block in a brother's way.
Once I realized that it was my business what days I observed or didn't observe, I also realized that when JWs judge one another (and everybody else) over such petty trifling matters it showed them for what they really were: false Christians.
The passage in Romans 14 was a truly liberating one for me. It made me realize that as long as I wasn't harming anyone else, that nobody had the right to judge me for observing any holiday that I wanted to observe.