First, don't look directly at the sun without proper eyewear. This should be common sense. A third grader knows this; you should too. But you may not have been aware of the fact that sunglasses are not considered proper eyewear for eclipse purposes. You need to have a special set of eclipse glasses or a solar viewer to look directly at a sun, even if it's already partially eclipsed.
And please, for the love of god (and your eyesight), do not cheap out and try to make your own eclipse glasses. Buy a pair, and make sure they're less than three years old and the lenses are in good shape. To confirm that they're a quality product, the manufacturer's name and address should appear somewhere on the glasses and they should have ISO 12312-2 certification.
Look, NASA isn't trying to ruin your fun. "While NASA isn't trying to be the eclipse safety glasses 'police,' it's our duty to inform the public about safe ways to view what should be a spectacular sky show for the entire continental United States," said Alex Young, associate director for science in NASA's Heliophysics department. They just want you to plan ahead and, you know, not go blind.
NASA's really going all out for this eclipse. They're planning on livestreaming totality and they are even enlisting all of you as citizen scientists to gather temperature data during the event. This is a once-in-a-lifetime event (that's happening again in 2024, but we won't talk about that right now) that you definitely should not miss, and also should definitely secure proper eyewear for.