Ino believes in happily ever afters.
To her, happily ever afters are a guarantee that no matter how bloody her hands get, no matter how many friends she loses, everything will be okay in the end. Everything can and will be set right. The light will always push back the dark, the sun will always rise and everyone will always get the happy ending they've always dreamed of.
If she stops believing in that, then she stops believing in everything.
What's the point if life will always be this dark, this painful, this horrible, this heartbreaking? Why should she fight, why should she try if all that will happen is that friends will die, hearts will break and she'll be left all alone in her misery? Why should she bother if it's just a waste?
And nothing's more terrifying to Ino then finding out it was all just a waste.
So Ino believes in happily ever afters because she has to, because if she doesn't…well she doesn't want to think about that.
In the world of the shinobi everyone has to hold on to something to get them through the day. Ino holds on to her belief in happily ever afters.
Because if she believes that everything will turn out okay, then she doesn't have to worry about what to do when it doesn't.
