It is an interesting thought as to why the first of the Ten Commandments is "Thou shalt have no other gods before Me." I've always been taught in Sunday School that this commandment was given because God is jealous and doesn't want us worshiping anybody/thing else. This kind of made sense, other than the fact that jealousy is usually a negative trait. In other classes this subject was made more clear when I realized that it's not just because God is jealous, but that he knows that he is the only entity that can ensure us eternal happiness. Anything we think is more important than God (particularly with regards to the activities we do on Sunday, those that distract us from the purpose of the Sabbath) will become our idol, our god.
President Spencer W. Kimball related a story about a group of men capturing monkey's in the jungle. They made small crates with a hole in it just big enough for the monkey to put his hand in. They then put a small nut in the crate that the monkey's liked. When the monkey's came out of the tree and discovered the crates with nuts in them, they reached in the box, grabbed the nut but could not pull their hand out because their fist was to big. Even with the hunters approaching them they did not release their prize. In the same way Satan is like the hunter, and if we go after the wrong prizes (clothes, homes, businesses, machines, automobiles, pleasure boats, degrees and letters and titles, power and prestige, the hunt, the fishing trip, the vacation, etc.) we will get that which we so desire at the cost of that which is of most value.
I would like to share a very interesting fact. If a man owns a million dollars worth of gold, he possesses approximately one 27-billionth of all the gold that is present in the earth's thin crust. The Lord who created and has power over all the earth created many other earths as well, even "worlds without number." How insignificant our earthly riches are when the Lord has promised those who have received the oath and covenant of his Holy Priesthood "all that my Father hath." (Doctrine and Covenants 84:38)
Joseph Smith's translation of Matthew 6:38 summarizes well this topic, "Wherefore, seek not the things of this world but seek ye first to build up the kingdom of God, and to establish his righteousness; and all these things shall be added unto you."