1)RESPECT FOR ONE'S CLOTHING VS ONE'S BODY
אמר רבי אלעזר שמעתי שהמקרע על המת יותר מדאי לוקה משום בל תשחית וכ״ש גופו ודלמא בגדים שאני דפסידא דלא הדר הוא כי הא דרבי יוחנן קרי למאני מכבדותא ורב חסדא כד הוה מסגי ביני היזמי והגא מדלי להו למאניה אמר זה מעלה ארוכה וזה אינו מעלה ארוכה
Translation: R. Elazar said: I heard that one who tears his clothing too much for a dead person is given lashes because of the prohibition of 'do not destroy.' And he would certainly be liable for injuring his own body. Perhaps clothing is different, since it is a loss that does not return? This is like R. Yochanan, who would refer to his clothing as 'that which honors him'. And Rav Chisda, when he would walk among thorns and thistles, he would lift up his garments to protect them from the thorns. He said: This (skin) will be restored but this (garment) will not be restored (as it will remain torn).
(a)Is one's clothing more important than his flesh?!
1.Lekach Tov: Even though it is usually worse to damage one's body than damage one's property, since the damage to the body here is only temporary (in contrast to the clothing), it is better to damage the body.
2.Shita Mekubetzes citing the Ramah: Yes, the Halacha follows Rav Chisda, that it is permitted to damage one's body, but not one's property. (N.B. Many Poskim disagree with this conclusion.)
2)R. ELAZAR HAKAPAR'S VIEW OF ABSTINENCE
אלא האי תנא הוא דתניא אמר ר״א הקפר ברבי מה ת״ל וכפר עליו מאשר חטא על הנפש וכי באיזה נפש חטא זה אלא שציער עצמו מן היין והלא דברים ק״ו ומה זה שלא ציער עצמו אלא מן היין נקרא חוטא המצער עצמו מכל דבר על אחת כמה וכמה׃
Translation: Rather, it is this Tanna who taught in a Beraisa: R. Elazar Hakapar B'Rebbi said: What does the verse teach us by saying, 'And he will atone for him, in that he sinned against a soul.'? It means that he has sinned in troubling himself by refraining from wine. And is it not a Kal Vachomer? If this Nazir, who only troubles himself to refrain from wine, is called a sinner, then certainly this is true of someone who troubles himself to refrain from everything?
(a)Why does the Pasuk refer to a sin 'against a soul'?
1.Toras Chaim: It is beneficial to the body to fast as it reduces the physical that is a cause of sin. However, it weakens the strength of the body to perform Mitzvos and learn Torah, which would have benefitted the soul. Therefore, the Pasuk refers to sinning "Al ha'Nefesh" - "against the soul".
2.Ben Yehoyada, Rav Tzadok ha'Kohen of Lublin: Since there are sparks of souls reincarnated in the food and drink, when one partakes of that food or drink and recites a Bracha, he elevates and releases those sparks. By refraining from eating and drinking, one sins against those souls as he does not release them.