About one hundred years ago a famous Jewish thinker stated that more than the Jewish people kept (observed) the Shabbos, the Shabbos kept (preserved) the Jewish people. Observing the Shabbos properly is the way we "testify" (and proclaim) that we believe in the story of creation. Once we accept that the Ribbono Shel Olam created the world, and all that is in it, then it follows that he is "baal ha'bus" ("the boss"), and all of His instructions are binding.
I was very saddened to hear that some writers were encouraging religious children in elementary and high school not to reject the dream of becoming a professional sports star due to concerns of not being able to observe Shabbos. These writers say that a Jew could simply rent a hotel room within the techum of the stadium where the games will be played to avoid carrying anything in the streets and then play their sport on Shabbos with their yarmulka on and thereby accomplish a fantastic "kiddush Hashem". This is absolutely incorrect!
The Rambam writes that on Shabbos we are instructed to observe four mitzvos. The two that appear in the Chumash are zachor and shamor and the two that are spelled out by the Navi are Kibbud and Oneg. If one avoids violating any melochos, he has fulfilled the mitzvah of Shamor, but he certainly has not fulfilled the mitzvos of kibbud v'oneg. Rav Soloveitchik zt"l has suggested that the Hebrew word which the Rambam used to explain that kibbud and oneg were spelled out by the nevi'im could well be understood to mean that the prophets interpreted that kibbud and oneg are included in the biblical mitzvah of zachor.
Kibbud v'oneg require of us that we dress, speak, and act in a Shabbos-dik manner, in a way indicating that Shabbos is a very holy day. Wearing bigdei Shabbos (Shabbos clothes) is extremely important in this regard. Dressing in sports clothing to play a professional sport for which a person is salaried is clearly a violation of kibbud and oneg. The violation of Shabbos is on several levels that are independent of each other: a) bigdei Shabbos; b) he's being salaried; c) the activity itself is not Shabbos-dik. We were given the gift of Shabbos to recharge our spiritual batteries!
An Orthodox young man who says that he will be wearing his yarmulka and will be playing professional sports on Shabbos will not be making a kiddush Hashem at all. If anything, this will constitute a chillul Hashem b'rabim; it probably would be better if he would not wear the yarmulka.
The Chumash tells us that Hakadosh Baruch Hu loved Avraham Avinu because he was mechanech his children properly to fulfill Hashem's mitzvos. Parents have a serious obligation to see to it that all of their children should observe Shabbos on all of its levels, not just on the level of issur melacha. Once one chisels away at part of Shabbos observance, it will not take too long before the other levels of observance will also fall away. We should not permit our children to "compromise" on any of the mitzvos of Shabbos, or on any other mitzvos either.
The possuk (Tehillim 10:3) states that one who praises an individual who compromises on mitzvos is compared to one who curses Hashem. The Torah (Devarim 7:2) has a mitzvah of lo si'choneim. The Gemara (Avodah Zara 20a) points out that there are three levels of interpretation of this mitzvah, and all three are accepted as biblical prohibitions. One of the interpretations is that the verb "si'choneim" comes from the root of "chein", thus indicating that we should not elevate nochrim to be our heroes whom we look up to and choose to emulate. The nochrim have a totally different perspective on the world than the Torah's perspective. The Jewish people live differently, die differently, and are buried differently. We just read in Pasrshas Chayey Sara about the halacha of kever Yisroel, i.e. that Jews may not be buried in the same cemetery as non-Jews[1]. Similarly, the Torah teaches us that our body is not our personal property, and thus we may not tattoo or mutilate our body. We live in a generation where so many Jews have picked up the attitude from the rest of the world that we have the right to do with our bodies whatever we choose. This is totally in contradiction to the traditional Jewish attitude. We say in Selichos "Haneshama loch v'haguf sheloch" - we are totally owned by, and subservient to, Hakadosh Baruch Hu, and must act in the unique way that He requires of Jews in every aspect of life.
The Gemara (Bava Metzia 83b) explains the possuk, "Toshes choshech v'yehi layla..." (Tehillim 104:20) to be a reference to olam hazeh (this world) which is similar to layla (night). In what way is olam hazeh similar to layla? The Mesilas Yesharim explains that it is very unclear if a lot of things in life are a mitzvah or an aveira, and we need the Torah to illuminate this darkness. We therefore request in our tefillos, "v'haer eineinu b'Torasecha", that Hakadosh Baruch Hu should illuminate this choshech (darkness) by having us succeed in learning Torah and figuring out what He wants from us.
The Mishna (Pirkei Avos, end of perek 5) instructs us, "Hafoch ba va'hafoch ba d'kula ba" - don't reinterpret the Chumash and the Talmud based on your preconceived notions and desires, rather study the Torah carefully and adopt the Torah's true values and attitudes.
[1] Editor: see Jewish Burial, by Rav Schachter.