Megan Hallinan has mushrooms nailed to her head:
You know how either as an adult, you see something dangled in front of you but you decide that it is not needed in the moment. So you carry on with your day assuming that this moment will be gone forever. But then it’s not. You have a un chiodo fisso—a single thought fixed in your mind.
Un chiodo fisso is such a lovely Italian idiom: there’s rarely a time I don’t have a single thought fixed in my head. Sometimes it’s a design for something, and the thought cannot be staunched until I make the thing, sometimes it’s a less helpful “if only X happens, everything will be better.”
Mindfulness is all the rage these days, enough to risk triggering my aversion-to-things-all-the-rage switch, had I not found it so darned helpful in navigating the emotional seas. Having a slight mindful remove from an unhelpful notion nailed to my head has proved a useful device for dislodging it.