What is one of the most common mistakes people make when getting prepared to fish?

Probably not preparing for the weather. It's going to rain sometimes. Always keep rain gear ready. Having backup equipment is also really important. Make sure you have two rods with you because things happen. Polarized glasses are an absolute must. Those allow you to see into the water. Mindset is the other thing to prepare. Go with a sense of adventure. Know that you're probably going to make mistakes, we all do. You might not catch fish and that's okay but you're going to learn something in the process and if you do catch fish, that's a bonus.