The Rambam codifies l'halacha (Talmud Torah 3:13) the famous derasha on our parsha on "Adam ki yamus b'ohel," that a person has to kill himself learning in order to succeed.
אמרו חכמים דרך רמז, "זאת, התורה, אדם, כי ימות באוהל" (במדבר יט,יד)--אין התורה מתקיימת, אלא במי שממית עצמו באוהלי החכמה. וכך אמר שלמה בחכמתו, "התרפית, ביום צרה--צר כוחך" (משלי כד,י); ועוד אמר, "אף חכמתי, עמדה לי" (קוהלת ב,ט)--חכמה שלמדתי באף, עמדה לי.
Rav Shach asks an interesting question. One of the ingredients necessary to acquire Torah is "yishuv ha'da'as." Chazal tell us, "Shamytza ba'ei tzilusa" -- learning demands a clear head. How can you have yishuv ha'da'as while at the same time killing yourself? How can you have yishuv hada'as while subsisting on pas b'melach?
The Slabodka mussar answer would probably be that the kashe gufa is itself the teirutz -- Chazal want a person to develop the skill to have yishuv ha'da'as despite the hardships.
My son suggested that there is a difference between interenal and external pressure. The Rambam is speaking of personal commitment, similar to his psak elsewhere that poverty, age, illness, etc. are not excuses for not learning. When Chazal speak of yishuv hada'as they mean freedom from outside interference.
Rav Shach (intro to Avi Ezri, Hil. Nashim) answers that unlike other disciplines, Torah is not acquired only through brains alone -- it must come as a gift from Hashem, and Hashem rewards those who invest self sacrifice and maximum effort in their learning. The appreciation that one has been given a gift directly from Hashem is the blessing of yishuv hada'as Chazal had in mind.
One final note: Someone who sees a person killing himself to learn might think why bother -- why choose to kill yourself when you can enjoy life. The answer is that such a life is itself misa, as the Rambam tells us in Hil Rotzeiach (7:1):
וחיי בעלי חכמה ומבקשיה בלא תלמוד כמיתה חשובה
It's only through the misa of adam ki yamus b'ohel that one can truly live.