It started as a joke. Ron knew Divination was just spewing out rubbish and making stuff up.
Then he realized it. It was not like being hit with a splash of water. But a slow dread that began to creep into his skin.
It was after the Battle of Hogwarts when he really began to notice it. Sometimes, he would say one thing. It would be just casual talk but sure enough, he realized it had happened. Deja vu, intuition, Hermione always had some other explanation to convince him.
He could've prevented things, warned people. He did try to warn some, but it was useless. The very act of warning sometimes became the cause.
Then it got worse. He started to see people fight, get injured, dying. A little girl, he saw losing her parents, he didn't know who she was. Only later, when accompanying Harry to Dudley's funeral, did he recognize the little girl.
Harry realized why Ron was being too friendly with his little niece. Uncle Ron, the little girl said, always did good tricks and had funny stories to tell. Harry accompanied him to see Trelawney, who was barmy as always. But strangely Ron became more subdued after that.
He predicted and helped to prevent many dark lords from showing up. He became a new idol, a different one than his friends. For the first time in several years, Divination became significant.
Ron began to show dark circles under his eyes. He spent long nights, writing everything he saw. Clear documentation of every vision he had, every possible prediction triggers. Locations, names, dates, times, everything went into record. There were dates of several years into the future, predicting massacres and miracles across time, far ahead in fact. They weren't sequential, though. Hermione helped him greatly, and after months, his work was ready to be published.
But Ron never came out of his room, on that day. They found his body, his face showing guilt. Anyone who knew him never wished upon that fate for him. On his desk was a letter. In it, was his last prediction, his own death. He also left a note to his sweet niece, the message read, "The future, it's truth is a beautiful and terrible thing. Take caution, dear"