Is it necessary to repeat the prayers that were previously performed without khushu' (devotion) and طمأنينة (tranquility), due to ignorance of the ruling? And how can one distinguish between a lapse that can be rectified by the prostration of forgetfulness (sujud as-sahw) and the lack of tranquility that invalidates the prayer, especially with the presence of obsessive-compulsive disorder (OCD) and evil thoughts during prayer?

Tranquility (al-Tuma'ninah) is one of the pillars of prayer, achieved by the stillness and settling of the limbs in every physical pillar [of the prayer]. As for devotion (al-Khushu'), it is the presence of the heart in prayer and is considered desirable by the majority of scholars. A Muslim must strive against the whisperings of Satan and not cut off their prayer because of them. As for the prostration of forgetfulness (sujud al-sahw), it is prescribed when there is an addition or a deficiency in the prayer, and when in doubt, while building upon the lesser (more certain) number. However, if doubts become frequent to the point of obsessive whispering, then the prostration of forgetfulness is not prescribed.