I get the sense that his heart wavered for a second and he does not want to be so emotionally affected by her so he's pulling back to keep his distance. However, he's gonna miss out on a lot of things if he keeps up this attitude. There's only so much that girl can take.
I think hes saying that her smiles are bad for his heart. Specifically that he might become to invested in the princess. His long term plan probably involves marrying someone else either before their marriage is finalized or sometime shortly therafter
Hmn.. I like the little brother more
Well let's just hope for character development for down XD
Can't wait to see him express his feeling more freely in the future