At the other end of the emotional spectrum, Amos 8;10 spoke of the first day of mourning as sad/bitter, leading the Gemara to exempt a mourner on that first day, because tefillin are a marker of pe’er, splendor, contraindicated on such a day. After the first day, the mourner does put them on, and would not take them off even if panim chadashot came, a new person with whom this mourner has not yet commiserated.
Normally, panim chadashot rejuvenate a lifecycle experience, the happiness of a wedding or the sadness of a loss. For tefillin, we apparently do not think the emotions raised by seeing the new person negate wearing tefillin. AH does think a mourner should wait until the panim chadashot person leaves before putting on tefillin, but I have not seen this done, perhaps because we have restricted tefillin so fully to the world of the ritual.
We might think a mourner counts as mitzta’er, someone in distress, for whom tefillin are an added bother. AH thinks mourning lasts long enough for it to be untenable to apply this status the whole time. Tisha B’Av morning, he says, we are too enveloped in our recalled national tragedy to don tefillin, but by Mincha the pain has worn off somewhat, and we put them on. Se’if fourteen notes that mitzta’er includes all sorts of pain that disrupt full concentration. Theoretically, someone who is cold or has pain in their teeth would be exempt, although AH doesn’t think we act that way, for reasons he does not know.
