More first-time mistakes: the ones nobody warned you about

Thinking about the session while in it. I spent 90 minutes of my first session worrying about whether the session was going well. This meta-cognitive loop is self-defeating and very common. The preparation that I now give to people: the session is happening regardless of your evaluation of it. You cannot optimize it in real time. Notice that you're noticing, and return to the experience.

Checking your phone. Even once. The outside world's information, especially bad news or social media, enters the session and doesn't leave easily. The phone stays in another room or in a bag. This is non-negotiable advice that I've given and violated and regretted.

Not telling your sitter specifically what you need. General 'be there for me' doesn't communicate: Do I want conversation or silence? Do I want you to check in or wait for me to initiate? What should you do if I seem upset — sit closer, speak, or leave me be? A 20-minute conversation about this before the session is worth more than any other preparation.