Complex sentence: Fievel is unsure about taking it, since he feels he is not a traditional hero, but Wylie reminds him that, if it weren't for Fievel, he'd still be a washed up dog.
Split into simpler sentences: Fievel is unsure about taking it, since he feels he is not a traditional hero. However, Wylie reminds him that, if Fievel did not meet him, he would still be a washed up dog.