Stress can cause heightened anxiety which can cause increased stuttering. Aside from the great advice from other people, listen to motivational videos from people that have overcome adversity. I used to listen to David Goggin to lift myself up. Try different herbal supplements for anxiety and experiment one at a time. I take ashwagandha when I’m stressed, and it helps calm me down. Sleep well. Sleep is your superpower. I like to listen to Brian Cox or other science narrator with soothing voice to help me fall asleep. And don’t isolate yourself from people. We’re designed to be social animals. Being social helps us regulate our mood and stress levels.