I ruminate a lot! I wish I knew exactly how to stop it.

You will have times where you'll forget a word or say something incorrect. Everybody makes mistakes. People don't hate others for making a mistake. Some will relate to it and try to help you. They won't be doing it to criticize; they will likely be trying to help. Others might ignore it or ignore you. I would try to 'reframe' how I plan to respond.

Imagine you are in the store and forget a word. Now, think about how you can respond in a different way. Don't let yourself feel criticism or judgement. Let it pass through you. It only hurts if you let yourself feel it. Most people are too concerned about themselves to worry about a stranger anyway. You might respond instead by telling them you are learning French and need help with the word. Or, just ignore the mistake and move on. When I am with strangers, I try to imagine people are my friends even if I haven't met them. It is just a trick to take away the anxiety of the unknown in interacting with them.

I hope your trip is wonderful.