The success of others do not dictate your failures. Your past ensures a great and heavy example, or lesson, of how to climb over your current doubt, fears, and blockades.
To me, this powerful image seems like a much older Levi is wishing he could, in some way, reassure his younger self that he would rise up from the squaler that seemed to be his fate at some point. Because that was the supposed fate of a whore mothers bastard child.
Despite the abandonment, all the pain and sacrifice, he made it as far as to be considered a seasoned soldier, a captain, and was given the title of 'humanities strongest'.
He didn't end up as a corpse underground struggling to make due with the little he had, despite the presence of his loyal friends. He rose above it, became someone important to an entire species, and when he's gone, he'll have a name. He existed, and not in the wrong frightened dim of light.