Write about something that seems absolutely impossible, and imagine the ways in which it could be done if it absolutely had to be done. That impossible thing could be a career goal, a heroic feat, building a technology that doesn’t yet exist…. anything.
If it’s helpful— because let’s be real, this is kind of a big and weird one— start by making a list of things that seem impossible to you. Then pick one and start imagining all the ways in which it could happen anyway, and see where the writing takes you.