Towards the beginning of Parashat Toledot we read of Esav's "sale" of his birthright to Yaakov in exchange for food. In narrating this incident, the Torah offers us a glimpse into Esav's thought-process as he agrees to this transaction: "Behold, I am going to do die; for what do I need the birthright?" (25:32). The commentators offer different approaches in explaining Esav's intent in this remark. Rashi explains this comment as a reference to the numerous and demanding laws governing the sacrificial service, the responsibility towards which were to fall on the shoulders of the eldest son. Yaakov informed Esav of the many prohibitions involved in this ritual service, many of which are punishable by death. Esav thus exclaims, "Behold, I am going to die!" He feared his inability to maintain the strict standards entailed in the responsibilities of the birthright, and therefore gladly rid himself of this burden in exchange for Yaakov's stew.
Rashi's reading of this verse should perhaps be understood in light of the phrase with which the Torah concludes this narrative: "Va-yivez Esav et ha-bekhora" ("Esav scorned the birthright" – 25:34). In theory, one can interpret this clause in one of two ways. First, one might suggest that in the spirit of the Aesopian "sour grapes," Esav denigrated the birthright in order to retroactively rationalize his sale of the birthright. Recognizing that he forfeited an eternal privilege in exchange for momentary gratification, Esav convinced himself of the worthlessness of the birthright he had just squandered, thereby consoling himself for having made this decision. Alternatively, however, the Torah here perhaps offers some clarification regarding the sale, informing us that Esav forfeited his firstborn privileges because he "scorned the birthright," meaning, because he did not afford it any value. According to this reading, this verse should be understood to mean, "This all happened because Esav scorned the birthright." This appears to be Rashi's intent in his commentary to this verse: "The Torah testified to his sinfulness, in that he scorned the service of the Almighty." Rashi seems to explain that the Torah here testifies to the fact that what had just transpired resulted from Esav's contempt for the birthright.
This "testimony" of the Torah concerning Esav's squandering of the birthright sheds light on Rashi's earlier comments, regarding Esav's fear upon hearing of the responsibilities associated with the status of firstborn. The Torah here instructs that excusing oneself from a certain task that appears too daunting and demanding effectively amounts to disregarding the importance of that task. The attitude of "It's too hard for me" often results from a lack of appreciation for the value of the given undertaking. A person who understands the importance of a task will be prepared to accept the challenges involved and commit himself to confronting them successfully. Esav explained his preference on the basis of his fear of the rigorous standards he would have to meet as firstborn, but the Torah testified that he in truth "scorned the birthright." Had he afforded this privilege the value it deserves, he would have accepted the difficult challenges involved, rather than flee from them.
(Based in part on Rav Moshe Feinstein's comments in Kol Ram, vol. 2)