the butterfly effect

all films of this kind offer us a way to know what's mental disorder. H killed the girl by mistake as they were young, but the guilty leads him into the deep since he can not confront the death of the girl. he rehearsed many times to change the result, which consists the entire film, and of course it's all in vain and hallucinative. what gives us the real information is the conversation between the doctor and his mother in almost the end of the film. got it now?