I should have known better. 

I should  have known better than to lash out.

I should have known that it's better for me to keep my emotions to myself only.

I should have known that people will get tired of me once I get too hard for them to handle.

Anyway, the person who said "don't let their words get to your head" had probably never been hit by words as sharp as hundred knives thrown together all at once.