What is something important you've told someone, but they refused to believe you?

What is something important you've told someone, but they refused to believe you? I'll go first. You could learn more about marketing from one website than you can a four year $200,000 degree from any university. Especially for visual learners like me. It's called marketingexamples.com. Literally just marketing examples. They've curated all of the best marketing examples broken out by each channel. So giveaways, cold email strategies and content, referrals, pricing, even different copy for landing pages, all on this website. And it's all free. My favorite is this. They bookmarked the 17 best copywriting examples that I look at every single time before I write copy for any client or even my own website. This one is fire. No one cares what you do. Everyone cares what you do for them. Don't say the world's first portable digital media player. Say a thousand songs in your pocket.