فَإِذَا قَرَأۡتَ ٱلۡقُرۡءَانَ فَٱسۡتَعِذۡ بِٱللَّهِ مِنَ ٱلشَّيۡطَـٰنِ ٱلرَّجِيمِ (٩٨) إِنَّهُ ۥ لَيۡسَ لَهُ ۥ سُلۡطَـٰنٌ عَلَى ٱلَّذِينَ ءَامَنُواْ وَعَلَىٰ رَبِّهِمۡ يَتَوَڪَّلُونَ
Shaytan has authority over those people who do not rely on Allah.
Regrets and constant stress are from shaytan. In fact, most psychological disorders like anxiety, stress, depression, are a manifestation of waswasa (whisper of shatyan). The Qur'anic remedy for waswasa is tawwakul (trust in Allah).
In times of trouble and difficulty, say: I trust Allah, there must be some good in it.
When there is a lack of tawwakul, we get confused, and constantly bombarded with questions, fears and panic attacks from shatyan. We are held hostage by our own nightmares and pessimism. The remedy to this is recitation of the Qur'an. Allah's Words not only soothes the nerves and relaxes the mind but also counsels those seeking therapy and closure. Read the Qur'an and let Allah tell you that He is with you, you are going to be okay.
Qur'an, 16:98-99