Well, in the story Hal was starting to wonder what it meant to be 'a man without fear' (having a studio audience laugh at the very concept and being completely unaffected by 'fear' when he was being attacked by an enemy targeting his emotions probably had something to do with it).
Eventually he asked the ring, and the ring replied he was fearless 'as per instructions.' Apparently Abin Sur requested someone without fear, but the ring was unable to find anyone who matched that criteria (at least anyone who was sane), so it was forced to find someone with a minimal amount of fear (Hal Jordan) and change him to suit Abin Sur's instructions. Hal demanded the ring return him to his previous state and it complied. Hal subsequently fell out a window when attempting to fly. Thankfully watching him struggle to overcome his fear and fly to safety inspired the suicidal man he was attempting to rescue to climb off his ledge and seek help.