Psychologically, every loss is damaging to a boxer. But some losses are far more damaging than others. It all depends on what stage the fighter is at in his career. And his ability to re bound after being beat may tell us a lot regarding how that defeat has affected him. What examples do you have of some boxers' defeat from which the fighter in question either never recovered, or was never the same? Some just right off the top of my head... Vargas / Tito Tito / Reid Tyson / Douglas Vernon / Mayorga to a certain extent? Arguello / Pryor Taylor / Chavez Zarate / Zamora Any others?
Foreman/Ali (took big george 20 years to get over that) Judah/Tszyu Grant / Lewis (Lennox broke that man, and all of Teddy Atlas' horses and all of his men couldn't put Mikey together again) Jones/Tarver (Roy became timid and gunshy after Tarver put his lights out)
Hagler vs SRL Tito vs Hopkins I dont think Lacy was as mentally beat down by his loss to Calzaghe as people think he was
Zarate got so disgusted after losing a highly controversial fight to Pintor that he didn't fight again for like 8 years.
reid v tito judah v spinks (spinks was in his hometown and came in rappin with nelly and got knocked out) hopkins v tito gatti v mayweather