Yet another quote that zillions of people have repeated all over the web, with no one giving a source. It's attributed to Jonas Salk, and the two main variations I've found are:
I have had dreams and I have had nightmares, but I have conquered my nightmares because of my dreams.
I have had dreams and I have had nightmares. I overcame my nightmares because of my dreams.
Wikiquote cites Wisdom for the Soul: Five Millennia of Prescriptions for Spiritual Healing by Larry Chang, and Google Books shows the quote on page 254. The Wikiquote version and Chang's version differ from each other and from both the versions above.
Does anyone know whether Salk actually wrote or said some such quote, and where? I'm not prepared to take Larry Chang's word for it when he doesn't cite a source.