I never sleep well the night before a therapy session either and judging from the psychotherapy forum, we are not unique. Getting value out of therapy requires discussing hard things/things you have never or rarely discussed. Inevitably, I end of thinking about how to put it into words prior to a therapy session and thinking about it causes anxiety. And I feel anxious about it a night or two or even for a whole week after but it does seem to help in the long run. So if you can find someone who you can eventually talk to about uncomfortable things, I think it will help you. Good luck today!