Albus Dumbledore once said “Indifference and neglect often do much more damage than outright dislike.”
This quote was spoken in HP& The Order of the Phoenix, and I honestly don't remember the context, but I DO know that it's great love advice. Seriously.
Take Ron&Hermione for instance: sure, they were kind of falling in love with each other all along, and maybe Hermione had realized it before Ron, but that was OK. It wasn't OK once he began to neglect her as a friend and became indifferent to her emotions, though. In fact, if he had hated her, or told her that he didn't love her, then she would have been able to get over it much, much easier. Instead, though, she was left to suffer while she watched Ron frolic around with Lavender. And nobody like a frolicker.
How can we learn from this? Don't frolic with girl's named Lavender.
But also, don't neglect those you care about. Don't treat anybody you wish to date (or be friendly with, or otherwise) with indifference. Because it will hurt the relationship in a way that cannot be easily resolved. When you say "I hate you!" the words can be taken back or changed as feelings do, but even if you assure someone you care about them after months of indifference, the change won't be as easy to believe.
So, make sure to pay attention to those you care about: don't neglect their love or affection!