Nearly 40 years ago, the Rabbi of a shul in England told me that the mother of a boy who had had his Barmitzvah on the previous Shabbos,  had proudly told the Rabbi that her son had put on his tefillin before going to shul that Shabbos! I later spoke to this boy and said to him that surely he knows that one does not put on tefillin on Shabbos. He answered that he knows that, but considered that the Shabbos of his Barmitzvah was an important occasion and therefore he put on tefillin. There is an “upside” to this incident and that is that the boy saw the importance of the mitzvah of tefillin. This reminds me of the incident when Rav Levi Yitzchak of Berdichev saw a man oiling the wheel of his cart whilst wearing tefillin. Rav Levi Yitzchak said “Look how the man loves the mitzvah of tefillin, that even when he oils wheels he does not remove his tefillin.” I hope that after all these years this Barmitzvah boy is still laying tefillin – every weekday.