Merry Christmas...why?

I'm sitting here at school trying to do some work. This post is evidence that not much is getting done. Why? Because I"m having profound thoughts. Why is christmas merry, but thanksgiving is happy? Can Thanksgiving not be merry? Are birthdays not a merry occasion? In essence, both words mean the same thing. So why is it that Christmas is merry, but birthdays, Easter and Thanksgiving are happy?
My first thought is that it has something to do with syllables. Christmas has two, as does birthday and Easter, while Thanksgiving has three. With that logic, both birthdays and Easter should be merry.
Maybe it's letter configuration. Christmas ends with a consonant, as does Easter and Thanksgiving. So does birthday for that matter. But let us forgo what we learned in fifth grade (stay with me). Y is only a vowel in words that don't contain a vowel anywhere else in the syllable, i.e. words like syllable(syl·la·ble) and physics (phys·ics). Let's forget that and pretend for a moment that birthday ends in a vowel. That, then would make birthdays happy, but Thanksgiving and Easter merry.
Let us now consider how many letters are in each word. Christmas has 9, Thanksgiving 12, birthday 8 and Easter 6. Christmas is the only word that contains an odd number of letters. That, possibly, may be the link we are looking for. Maybe only odd lettered holidays can me merry. That means Hanukah, depending on how you spell it (Hanukkah, Chanukah or Hanukah) should be merry. Presidents Day (if you include the day), merry. Martin Luther King Day, merry.
But that brings me to another thought. What constitutes a holiday? If we assume that it's not having to attend work, as with Christmas, birthdays and other days in which missing work could get you fired, are not considered holidays. But what about Easter? Easter is on Sunday. Most people don't have to work on Sunday so technically you wouldn't have to work on that day, but would you if it were, let's say, on a Monday? I don't know. Since Jesus rose from the dead on that day I'm going to go ahead and assume that he would want us to have that day off of work.
And Christmas is Jesus' birthday, but what about your own birthday? Let's say you're one of those, I-celebrate-at-12-the-night-before birthday people. Let's assume that you plan on getting plastered and not going in to work. By my logic, that planned taking off makes your birthday a holiday. If you just get drunk and don't feel like coming to work, then your birthday is no longer a holiday, just an excused absence.
What about characters. Christmas has Santa Clause, Easter has a bunny, and Thanksgiving has a turkey. Your birthday has no mascot; therefore, your birthday is not merry.
Ok. I'm a little delirious from not sleeping, and I imagine I could keep going all day. I'm going to go ahead and assume that there is no rhyme nor reason that Christmas is merry and Thanksgiving is not. But, considering i just wrote all this, I'm going to try and make some sense out of it--a postulation if you will. Your birthday is only merry if you, without being fired, get off work and choose to recognize y as a vowel, and/or you have adopted some sort of mascot that would give you gifts (like the birthday aardvark). Thanksgiving is merry by virtue of being an actual holiday. Though Thanksgiving has a mascot, it does not deliver gifts. Thanksgiving can't be a holiday based upon the gift-giving-mascot clause, unless you count the pilgrims and Indians. Since none of us were alive then I'll go ahead and scratch that. Easter is only merry based upon its syllable structure and the gift-bearing mascot. We're going to forgo the absence of work because it's on Sunday. If, however, you believe that if Easter were on Monday you wouldn't get the day off (because Jesus would want you to), Easter is doubly merry.
This is stupid