The sources from the Rational Optimist Society highlight the importance of optimism in facing a changing world. The first source focuses on the potential of technology to solve real-world problems, using the example of XRAI glasses, which can help deaf people understand conversations in real-time. The second source celebrates the founding of the University of Austin, a new university focused on free speech and meritocracy, and encourages readers to embrace a mindset of optimism. The third source argues that while the world is generally improving, communism can have devastating consequences, as seen in Venezuela.