The naggy one

I really don't understand why I keep trying to correct my dad's behavior. It's not like he actually listens and changes. In the end, I am the one who gets frustrated and become the bad guy, the "naggy" one.

Example scenario from tonight:

After dinner, I saw dad grabbing two apples to peel.

Me: I don't want an apple.

Dad: It's for mom and I.

Me: Mom doesn't like eating apples after dinner. You did this multiple times before and she told you that she doesn't like it.

Dad: If I peeled it then she'll has to eat it. The apples are crunchy and sweet.

Me: It's not about how good the apple taste, she's full after dinner and she doesn't want it.

Dad ignores me and keep on peeling the apple. He gave it to mom after she came downstairs.

Mom: I don't want it. I am full and I just brushed my teeth.

Dad: Eat it, it's crunchy and sweet.

Me: I told dad that you didn't want it.

Mom: Ricky, help me eat half of it.

Me: No.

Then I started to gloat/nag my dad to which he ignores and call me a nag. I started to get frustrated because I told him it would happen but he seldom listens. I vowed to myself more than once that I will not do it again but I still do it every time. The scenario frequently ends with me frustrated and snappy with him ignoring all of what I just said.

Please, I beg of myself, don't do this to yourself anymore. Let him do what he wants.