It's good that you recognize this situational variance. Now that you do, instead of just focusing on the tools they offer in your speech therapy sessions, you can also just focus on how you FEEL. Take note of your breathing, your posture, everything about the way you are in the sessions. Really tune in to how relaxed you are. Then in other situations try to replicate that state. Maybe even find an object or phrase to anchor you to that state, something you can return to in other contexts. Goal now should be to experiment with bringing that state into other situations.