Hawzah News Agency – Imam al-Rida peace be upon him says:

إنَّ لِلقُلوبِ إقبالاً وإدباراً، ونَشاطاً وفُتوراً، فإذا أقبَلَت بَصُرَت وفَهِمَت، وإذا أدبَرَت كَلَّت ومَلَّت، فَخُذُوها عِندَ إقبالِها ونَشاطِها، واترُكُوها عِندَ إدبارِها وفُتورِها.

'Hearts draw near and turn away, and become active and frigid. When they draw forward they see and understand, and when they fall back they become dim and weary. Therefore, make use of them when they draw near and are active, and leave them when they are feeble and weary.'

Source: Bihar al-Anwar, v. 78, p. 353, no. 9