Process over destination

If you can't see a finished piece in your head, you can't chase it, so some people with aphantasia end up working by response: make a mark, listen to it, make the next decision. That shifts the creative focus from outcome to process. You can use it on purpose. Set a timer, decide nothing in advance, and make each choice from the one before it. Let the piece show you what it is. Many people find it takes pressure off, since there's no gap between a mental image and the real result to feel bad about.