Halacha is strict about guarding your life: ‘venishmartem me’od lenafshoteichem’ (Devarim 4:15), and the Gemara warns you not to stand in a dangerous place saying a miracle will save you (Shabbat 32a). So where’s the actual line? Are skydiving, motorcycles, or contact sports forbidden, or is a normal level of risk permitted – and is ‘danger’ measured objectively, statistically? Connected to that, the Gemara in Bava Kama (90b-91a) says a person may not injure himself. Is elective cosmetic surgery then self-harm, or permitted? Does the patient’s consent or psychological benefit change the din?