The Prophet sallahu alayhi wa salam said:

ما من القلوب قلبٌ إلا و له سحابةٌ كسحابةِ القمرِ ، بينما القمرُ يُضيءُ إذ عَلَتْه سحابةٌ ، فأظلَم ، إذ تجلَّتْ

“There is not a heart from the hearts except it has clouds like the clouds of the moon. If the clouds cover the moon when it is shining, it turns dark and when it goes away it appears”

[Saheeh Jami no. 5682]

Imam San’aani rahimahullah said:

“That is the hearts. Sometimes it is bright and the meanings are recalled and it remembers its Lord. Sometimes is is dark and does not realize anything”

[Tanweer Sharh Jami as-Sagheer]

Imam al-Munaawi rahimahullah said:

“The reason for the Hadith was mentioned in al-Firdaws that Umar asked Ali about a man who is speaking, then forgets [what he is saying], then remembers. So Ali said he heard the Messenger sallahu alayhi wa salam say the following narration”

[Fayd ul-Qadir (5/466)]

This is very interesting as it explains that phenomena when we suddenly forget what were saying in a middle of a conversation. The full narration mentions the following:

Ali said radiallah anhu said:

وبينا الرجل يحدث الحديث إذ علته سحابة فنسي ، إذ تجلت عنه فذكر

“While a man speaks some speech, the clouds cover [his heart] so he forgets. When it clears, he remembers”

[Reported by at-Tabarani]

Translated by

Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan

So instead of complaining or worrying about why we forget during our conversations or what we were about to say, we should just let the clouds pass. Subhanallah!

May Allah grant us beneficial Knowledge