When my son Aaron called Friday night and invited me to his birthday dinner, I cried after we hung up.It was such a small thing to say. “Mom, come over tomorrow. I want you there.”But for the past few years, ever since he married Vanessa, I had been getting smaller pieces of him. Holidays were “too busy.” Sunday dinners stopped. The grandkids waved at me through the car window more often than they ran into my arms. I kept telling myself that was normal. Grown children build their own lives. Mothers step back.