When the Prophet ﷺ wished to sleep, he would put his right hand under his cheek and say: “Allāhumma qinī ʿadhābaka yawma tabʿathu ʿibādak.” (Abū Dāwūd & Tirmidhī — ṣaḥīḥ). He said everyone is raised upon the state he died in. (Muslim) — so seal your day with this.
العربية: عن حذيفة رضي الله عنه أنّ النبيّ ﷺ كان إذا أراد أن ينام وضع يده تحت خدّه ثم يقول: «اللهم قِني عذابك يوم تبعث عبادك». (أبو داود والترمذي).
As your last words before sleep, ask Allah to save you from His punishment on the Day He raises His servants.