I don't think that learning the story behind why we celebrate Christmas necessarily means that it is in anyway less enjoyable to observe the tradition. I've celebrated Christmas for the past 21 years and i will continue to do so. For me it's a festival of giving gifts, family gathering and generally relaxing and enjoying something at the darkest coldest time of year. It's great!
This video from BeardyMan (a professional beatboxer) explains a lot of it in a short time and is quite funny (I recommend the uncensored version though).
The Date of Christmas:
The first evidence of the end-of-year festival came from Egypt with Pagan customs centred around the January calends. Christ-mas (as in the celebration of Jesus' brith) was created in the fourth century and then the date of the 25th December was set in the 5th century by the Western church to coincide with the day of the birth of the Roman god Sol (sometimes referred to as Ba'al, Mithras, Saturn and many other names from different periods of hsitory). Many historians have speculated that this was a deliberate attempt to convert Pagans to Christianity.
Biblical 'evidence' that Jesus was not born in December comes from Luke 2:8: "...there were in the same country shepherds abiding in the field, keeping watch over their flock by night." The Bible later claims that the winter is a rainy season which would not permit shepherds to abide in open fields by night (Solomon 2:11 and Ezra 10:9, 13).
There is no widely accepted true date of Jesus' birth, but estimates put it somewhere around September. If God had wanted us to celebrate Christmas, why would he have hidden the date from us so well?
The Spirit of Christmas
The spirit of Christmas that we know and observe now is a celebration of the birth of Jesus and a time to be thankful, to love thy neighbour and to give to the needy. The Pagan festivals of Saturnalia and Brumalia which came before and on December 25th respectively were festivals of merrymaking and worshiping the Sun God. It was not a huge leap for the church to procliam that the day of worship for the Sun God was actualy the day of worship for the Son of God. The rituals of the pagan festivals were so deeply ingrained in culture at the time that it would have been impossible to reject them and follow only Christianity, so this compromise was reached which is maintained today.
Christianity typically celebrates and observes the date of important figures' deaths. Paganism is the religion which observes Birthdays. My recent 21st birthday dinner was actualy a Pagan festival! Who knew?
Customs and Traditions of Christmas:
Mistletoe: - originally thought to be sacred of the Sun God by pagans and used for it's healing powers, mistletoe was hung and Pagans kissed under it as one of many debaucherous customs during the festival. The kiss was meant to celebrate the death of the old sun and the brith of the new one.
Yule-Log: - 'yule' meant 'wheel' which was a symbol of the sun god. If you were in cornwall, you may have used the term 'Stock of the Mock'. Devon and Somerset inhabitants might have used 'The Great Ashen Faggot'. All these were literally logs burnt as part of the festival. Yule-tide was actually a germanic pagan sacrificial feast that was later absorbed into Christmas.
Christmas Trees: - Orginally from Germanic Paganism in the 16th Century. Trees were decorated with fruit and nuts and children were allowed to collect them on Christmas day. Some fundamentalist Christians cite the following passage from Jeremiah 10:1-5 as biblical 'proof' that Christmas Trees are a banned practice:
 Hear ye the word which the Lord speaketh unto you, O house of Israel:
 Thus saith the Lord, Learn not the way of the heathen, and be not dismayed at the signs of heaven; for the heathen are dismayed at them.
 For the customs of the people are vain: for one cutteth a tree out of the forest, the work of the hands of the workman, with the axe.
 They deck it with silver and with gold; they fasten it with nails and with hammers, that it move not.
 They are upright as the palm tree, but speak not: they must needs be borne, because they cannot go. Be not afraid of them; for they cannot do evil, neither also is it in them to do good.
In reality it is more likely that this passage refers to the creation of false idols from wood, silver and gold. 'Christmas' trees weren't in use until around the 15th and 16th centuries and even then weren't specifically related to Christmas.
Father Christmas: - Also known as Santa Claus or Saint Nicholas. Saint Nicholas of Myra was a Turkish Bishop who was the subject of a legend about throwing bags of gold down people's chimneys to act as a dowry to allow three girls to marry and not become prostitutes. Strangely we leave that bit out when we tell the story to our kids!
Many parallels have been drawn between Santa Claus and Odin, a hunter God of Germanic Paganism. He was said to lead a hunting party through the sky, much like Santa and his reindeer. Children would place their boots near the chimney filled with carrots and straw for Odin's flying horse to eat. Their gifts would be replaced with sweets in a reward of their kindness.
The name Santa Claus actually comes from the Dutch 'Sinter Klaas' which simply means Saint Nicholas.
In Britain, however, we have Father Christmas who is a more general figure of Christmas with many of the same charateristics. He is said to live in Lapland, rather than the North Pole where Santa Claus lives.
Contrary to popular Belief, the Coca-Cola Company didn't invent the jolly, plum, red and white, bearded man we know as Santa Claus. Their adverts popularised the image first given by Thomas Nast in Harper's Weekly. The orignal image of Santa and the ideas of the sleigh, reindeer, mode of entry (chimneys) etc. all came from a poem by Celemnt Clarke Moore published in the Troy, New York, Sentinel on December 23rd 1823. The poem was titled "A Visit from St.Nicholas" but is now more commonly called "The Night Before Christmas".
Interestingly, 'Old Nick' is often a name given to the Devil, also known as "The Deceiver".
Presents: - Gift-giving was also part of Saturnalia and although the bible does tell us that the three wise men brought gifts for the baby Jesus, no other gifts were exchanged. It was custom at the time to present a king with gifts on arrival. The wise men most likely arrived after Jesus' birthday anyway, as the passage states that they were seeking out the child who WAS born King of the Jews.
Therefore the 25th of December really belongs to 'Dies Natalis Solis Invicti' - the birthday of the unconquered sun. Why devote the day to one famous prophet of old times when you could devote it to a number of fictional sun gods and use it as an excuse to eat well, spend time with friends and family, exchange gifts, decorate our house and town and have a few days off work?
What could be we celebrating instead?
Saturnalia - Roman festival on the 17th December, extended to a whole week ending on the 23rd in later years, during which there is much drinking and marrymaking and social roles are reversed for a short time. Servants are served by their masters. Presents are exchanged and people greet eachother with "Io, Saturnalia!" — (Io pronounced "yo").
Brumalia - the ancient greek solstice festival in honour of Dionysus (known as Bacchus by the Romans). He was the God of wine, inspirer of ritual madness and ecstacy. If we do it the Roman way, Brumalia is a 30-day festival of drinking and merriment starting on November 24th.
So Io Saturnalia! Happy Brumalia and Merry Christmas!