"I find it extraordinarily difficult to just... relax. Sit on a bench and watch the clouds. [...] But even if I'm in that perfect scenario where there's nothing to do... my brain will just fill the void with absurd daydreams and rabbithole trains of thought."
This is the case for many (all?) people. I've found that you need to intentionally train your ability to not let your mind do this. I recommend this book for some exercises to help: https://www.amazon.com/Happiness-Mindfulness-Thich-Nhat-Hanh...