Are Satan's whisperings limited to religious aspects or do they include the affairs of everyday life, such as doubting the locking of the door, for example?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.

Undoubtedly Satan is man’s enemy, as stated in the Quran. Allaah Says: (what means)  {Indeed, Satan is your enemy; so make him your enemy.} [Quran 35:6]

Indeed this enmity is unlimited, and it includes both religious and  non-religious matters. He tries his best to embitter man’s life, especially Muslims’, in order to deprive them of happiness in this life and the Hereafter.

The only way for a believer to protect himself from Satan is to abide by the teachings of Islam, regularly recite the morning and evening legislated mention of Allaah which were authentically narrated from the Prophet, sallallaahu ‘alayhi wa sallam, and to seek refuge in Allaah and turn to Him in all matters.

Allaah Knows best.