Chodesh Tov!

Rosh Chodesh is a happy day -
(וּבְיוֹם שִׂמְחַתְכֶם וּבְמוֹעֲדֵיכֶם וּבְרָאשֵׁי חָדְשֵׁיכֶם (במדבר פרק י פסוק י

But also a solemn one, as we say in Mussaf: ראשי חדשים לעמך נתת זמן כפרה לכל תולדותם
based on the passk:
( וּשְׂעִיר עִזִּים אֶחָד לְחַטָּאת לַה' (במדבר פרק כח:טו

In this regard it mirrors Rosh Hashanna which is a fusion of celbration and solemnity, feasting and forgiveness. Rosh Chodesh is seen as a meeting point with God. To that end it is happy, but also generates feelings of trepidation, inadequacy, and a call to self-betterment and atonement.
In the current war situation, may we merit the fufillment of these verses. May God remember us and save us:

במדבר פרק י
(ט) וְכִי תָבֹאוּ מִלְחָמָה בְּאַרְצְכֶם עַל הַצַּר הַצֹּרֵר אֶתְכֶם וַהֲרֵעֹתֶם בַּחֲצֹצְרוֹת וְנִזְכַּרְתֶּם לִפְנֵי יְדֹוָד אֱלֹהֵיכֶם וְנוֹשַׁעְתֶּם מֵאֹיְבֵיכֶם:
(י) וּבְיוֹם שִׂמְחַתְכֶם וּבְמוֹעֲדֵיכֶם וּבְרָאשֵׁי חָדְשֵׁיכֶם וּתְקַעְתֶּם בַּחֲצֹצְרֹת עַל עֹלֹתֵיכֶם וְעַל זִבְחֵי שַׁלְמֵיכֶם וְהָיוּ לָכֶם לְזִכָּרוֹן לִפְנֵי אֱלֹהֵיכֶם אֲנִי יְדֹוָד אֱלֹהֵיכֶם: פ

9 And when ye go to war in your land against the adversary that oppresseth you, then ye shall sound an alarm with the trumpets; and ye shall be remembered before the LORD your God, and ye shall be saved from your enemies. 10 Also in the day of your gladness, and in your appointed seasons, and in your new moons, ye shall blow with the trumpets over your burnt-offerings, and over the sacrifices of your peace-offerings; and they shall be to you for a memorial before your God: I am the LORD your God.'