Rabbi Yehuda Hachosid wrote...

Nshei Chabad Newsletter / Rabbi Yehuda Hachosid wrote not to cut one's hair on Rosh Chodesh, even on Erev Shabbos, because it might be dangerous (Likutei Dinei Uminhogei Rosh Chodesh , Ch. 11 Par. 1).

Rabbi Yehuda Hachosid warned not to cut one's nails on Rosh Chodesh (Likutei Dinei Uminhogei Rosh Chodesh, Ch. 11, Par. 2).