Oh boy, I remember those disappointed feelings when my sons little by little went their own ways. It was hard and it hurt. But believe me, the best way to keep them is not to be clingy. You are doing the right thing by not showing your hurt.
Once your son marries, you will see...he'll come around again,...alot.
Still, enjoy your mother's day. Do something special for yourself.:-)
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A friend is a gift you give yourself.
-- Robert Louis Stevenson