Where my justifications might fail

“Right and wrong do exist. Just because you don’t know what the right answer is — maybe there’s even no way you could know what the right answer is — doesn’t make your answer right or even okay. It’s much simpler than that. It’s just plain wrong.” 

Where I spent so many hours convincing myself that I am right…
The BIG difference between convincing and knowing:
Isn’t this a strong reason to fear that I may be wrong?