Yeah there's a reason behind this. Our brains put subconscious value on words that we say, and that pressure to say them accurately induces blocks. That's why titles, names, phone numbers, etc, are so hard to say - there is more mental pressure to get them right and there is no way around those words If you speak without thinking, your brain has little to no time to prepare what you're going to say. That's why when reading or speaking, it's useful to always think of the *next* word instead of the one you're actually saying, or keep your eyes on the words ahead of the one you're actually reading. Your eyes and your brain should always be one step ahead of what you're speaking - you're quite literally playing a trick on yourself which makes it easier to overthink and screw up. If you tell someone not to focus on a word, they will ONLY focus on that word, which makes this strategy very hard, but you have to practice thinking ahead. It has helped me tremendously.