"[...]Behavioral explanations propose that paraphilias are conditioned early in life, during an experience that pairs the paraphilic stimulus with intense sexual arousal. [...] once established, masturbatory fantasies about the stimulus reinforce and broaden the paraphilic arousal." - Wikipedia
If one was Harry Potter, one would consider it entirely normal to have continued nightmares about the Third Task in the summer after the fact. What was not normal, however, was the feeling in Harry's gut when he woke up; a tension he could not identify.
At least, he couldn't identify it at the time. Midway through the summer, however, while preparing lunch in the kitchen at Privet Drive, Harry dropped a knife and -- with his Seeker instincts -- reached out to catch it, unthinking, and caught the blade in his palm.
Then he stood, blinking, down at the deep cut, watching red well from the line and drip-drip-drip onto the floor in loud, messy splatter. Mesmerized.
That night, having managed to will his hand uninjured with magic, Harry dreamt of the Third Task again; his gaze fixed on the way the blood poured from the cut in the crook of his elbow, where Wormtail had made it, even after the vial was pulled away.
He woke up sweating, flushed, and hard.
Oh, Harry thought, biting his lip. So that's what it was.