Complex sentence: When Donkey persistently asks why, he sadly confesses that everyone judges him before knowing him; therefore, he feels he is better off alone, despite Donkey's admittance that he did not immediately judge him when they met.
Split into simpler sentences: When Donkey persistently asks why, he sadly confesses that everyone judges him before knowing him. Shrek feels he is better off alone despite Donkey's admittance that he did not immediately judge him when they met.