I don't know - it just happens. I'll be talking about something particularly difficult, and my voice will choke up. Then the tears come. When I first started seeing my therapist and would cry, she would wait to see if I grabbed a tissue from the box beside me. When I didn't, she'd get up and grab one for me herself. Now, at even the slightest crack in my voice, she's there with the tissues.
She's so sweet. I'm so lucky to have her
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Only you can prevent neurotypical jerkiness!