If one was asked to determine which of the following hurts most; detaching an entire fingernail, removing an eye or an abdominal surgery, he would have zero interest in evaluating the pain level of each of those procedures in order to come to a decision. This is so, says Rav Wolbe (Alei Shur vol. I pg. 80), despite the fact that eyes and fingernails are not limbs upon which one's life is dependant. Nevertheless, the body feels an acute pain when it is missing any limb; even if it is not one of the vital organs.
In a similar vein, regarding the mitzvos we say in davening, "ki heim chayeinu - for they are our life." Together, all the mitzvos of the Torah create a spiritual "body." The Torah does not differentiate between the various mitzvos nor does it categorize their levels of importance, because the lack of even a single mitzvah causes a deficiency in one's spiritual makeup and a flaw in his spiritual "body."
The Torah contains mitzvos between man and Hashem and mitzvos between man and his fellow man. There are obligations to be fulfilled with one's limbs and others to be fulfilled in one's heart. Additionally, some mitzvos are constant while others are time oriented. The fulfillment of all the mitzvos together aids one in achieving perfection in this world and assures him an honorary portion in the next world.
Some people are naturally more outgoing and may have leanings toward performing chessed or toward loving their neighbor. However, they might be lacking in their performance of mitzvos between man and Hashem because they are missing that same level of inborn motivation. Others are disgusted at the thought of defiling their mouths with non kosher food, but they have no inhibitions about sullying their mouths with lies or lashon hara.
In this week's parsha the Torah implies explicitly that we are not to follow our natural tendencies in deciding which mitzvos to perform. The Torah commands us (Vayikra 19, 3), "A man should fear his mother and father." Rashi notes that in contrast, regarding the mitzvah of honoring one's parents the Torah the Torah gives precedence to the father, as it is written, "Honor your father and your mother." He explains that naturally a child fears his father more than his mother, but honors his mother more than his father. Hence, the Torah places an emphasis on fear of the mother and the honor of the father.
We read in Krias Shema, "So that you should remember and perform all of My mitzvos and be holy to your G-d." Through the performance of all of the mitzvos together one achieves the very purpose of Yetzias Mitrayim; that special connection to Hashem described in the following pasuk: "I am Hashem your G-d, Who has taken you out of Mitzrayim, to be unto you a G-d."