This as-told-to essay is based on a conversation with Michaeleen Doucleff, the author of "Hunt, Gather, Parent" and "Dopamine Kids," released on March 3. This story has been edited for length and clarity. Around the time my daughter, Rosy, was 4, we went to the beach. It was a really beautiful, sunny day, and I realized I couldn't enjoy it. She was having a great time building a sandcastle; I was sitting there checking my email, texts, and social media . I felt this little hum of anxiety. Was