The rabbinic comment is that you should not place five passages in the tefillin instead of four, take five kinds of plant on Sukkot instead of four, or have only three items where four are commanded (Rashi).
There are complaints these days that some people make Judaism harder by introducing new stringencies – as it were, acting as if Judaism did not have enough rules already.
True some Jews are becoming stricter, not out of masochism or intolerance but because of love of God. They cherish the commandments so much that where there is a stricter as well as a more lenient option, they prefer the stricter. This is only a problem if it makes people boast of their piety and denigrate those who think differently.
The real problem is with those who subtract from the Torah… not seven days of shivah but one; not two days of yom-tov but one; not 24 hours of Shabbat but only Friday evening; not the whole bensching but the short form or none at all; not a full agenda of Jewish living but an abridged version that may diminish further.
If the doctor prescribes medication, do we change the number of doses, or the strength of the medicine?
Since God, the Heavenly physician, has worked out a balanced diet and the correct dosage for spiritual health, why should we think we know better?