On Shabbos Chol haMoed, both of Pesach and Sukkos, we lein from Parshas Ki Tisa beginning from Moshe's statement/complaint (33:12):
רְאֵה אַתָּה אֹמֵר אֵלַי הַעַל אֶת הָעָם הַזֶּה וְאַתָּה לֹא הוֹדַעְתַּנִי אֵת אֲשֶׁר תִּשְׁלַח עִמִּי וְאַתָּה אָמַרְתָּ יְדַעְתִּיךָ בְשֵׁם וְגַם מָצָאתָ חֵן בְּעֵינָי
Moshe said to Hashem, "Listen, you said I should lead these people, but you haven't told me what help I have."
Rashi immediately asks that we do find that Moshe had been told (23:20) that Hashem would send an angel to guide Bnei Yisrael. Why was Moshe saying that Hashem hadn't provided any guidance?
Rashi answers that Moshe was not happy with being told that an angel would be sent. That wasn't good enough. Moshe was saying Hashem, "We want the real deal -- You need to lead us. I need you to tell me that you are going to do that or we can't move forward."
The Tiferes Yosef quotes from the Ishbitza that these pesukim speak to us every Yom Tov. Pesach and Sukkos always correspond with the change of seasons, which means a change of periods in our life. The Yamim Tovim give us the spiritual energy to make that change and move to the next stage of our growth.
Angels are described as "omdim," standing. They don't grow; they are fixated in one spot. On the one hand, this means an angel can never regress. An angel cannot know failure or suffer disappointment. On the other hand, it also means an angel can never become more than it already is at the moment of its creation.
So we have a Pesach (or a Sukkos), we gulp down that spiritual energy, we reach spiritual heights. There are some people who think to themselves, "Wow, I wish I could hold on to this forever." But that attitude is a mistake. We need the leining to remind us to reject the temptation of the malach, of "omdim." Like Moshe Rabeinu, we need to turn to Hashem and say, "וְאַתָּה אָמַרְתָּ יְדַעְתִּיךָ בְשֵׁם," as much as we gained from Yom Tov (so far) we want even more, we are never satisfied, we want to connect to Ain Sof with no limits.