Pride and Prejudice
It was their pride, and prejudiced against the idea that made the four of them strive to succeed at it. No one believed that one man should or even could fall in love with three girls, so they did everything in their power to make it true. Harry refused to acknowledge it, his pride not letting him bow to the will of others. He was in love, and not just with one person but with three. Ginny, Luna and Gabrielle were all amazing, beautiful, wonderful people. It was impossible for him not to love them. Ginny was so graceful and fiery, ready to stand up to her beliefs and not let anyone get in her way. Most people believed that Luna was a lunatic, completely insane and that nothing she said had any real meaning: but Harry knew that she was insightful and intelligent, she wouldn't have been sorted into Ravenclaw otherwise, and that she would fight for anything she believed in. Gabrielle was so daring, always ready to take steps that others wouldn't, always ready to walk the extra mile. It really was no wonder to him why he loved them, and nothing that the rest of the world said about that would stop him.