Lily Evans had always considered herself a realist. She knew that James Potter was scum, and that Severus Snape was her best friend. She knew that she was (or rather, was going to be) an incredibly powerful witch, and that her sister really was just jealous. She knew that she was an ace in every subject, and that it definitely wasn't her blood status that made her so very bright. She also knew that blood status could only matter to pricks like my Marauders and You-Know-Who, and not to her best friend Severus.
But everything she knew got flipped upside down when Severus spat a curse word at her in front of a crowd, when she was trying to help him. It was flipped when James punched him square in the face when he didn't apologize, casting his wand to the side. It was flipped when people whom she had never discussed blood status with treated her differently because they now knew hers. Her magic wasn't as good, and her marks were falling. Lily was struggling, and people began noticing. Remus nudged her awake when she fell asleep in front of her Charms book. Sirius got her pumped up for a Quidditch game, cheering alongside her in maroon. Peter got her to eat a good breakfast every morning, reminding her gently that it was the most important meal of the day. And James would sit next to her in front of the fire and ask her to help him with his Charms spells, as he was 'totally rubbish.' Lily, always the realist, knew that they were going out of their way to make her feel better, and started becoming a little bit more of a dreamer.
