20-month old with a serious sleep problem! Please help!?

My oldest son Diego has NIght terrors, and this sounds a lot like it. My pediatrician told me its nothing to worry about, that he'll outgrow it. But its terrifying for me. And upsetting for him. He's had them for over a year, and I've noticed a pattern. Anytime we change something in his life, they get worst. Like potty training, taking away diapers, etc. Also, it depends how much excitement he has in the evening. One of the worst nights happened after we went to a carnival! That night, he had horrible night terrors. I think all the lights, people, and noises were just too much and gave him nightmares. So try to avoid stimulation after dinner. Turn off the tv, read a book, take a bubble bath, give him a mage. Only calm things. Soothing. This is the best way I've found to manage them. He still gets them occasionally, but its not everyday anymore. BTW, they started at 12months for him, and he's 30 months now.