This is how Optimus expresses his concerns goes in Princess Twilight Sparkle.
[Optimus walks over to Twilight]
Optimus Prime: You know, I'm actually looking for to the celebration.
Twilight Sparkle: You are?
Princess Celestia: But why?
Princess Luna: Why do you show much concern?
[Optimus looks out the window to the spot where Megatron is]
Optimus Prime: For my brother, it has always been a celebration of my victory over Megatron, but for me. [sighs] It was just a terrible reminder that I had to banish my own brother.
Twilight Sparkle: What?
Princess Celestia: Tell us more, Optimus.
Princess Luna: Why did you banish your brother?
Optimus Prime: Well,