Ibn al-Qayyim – rahimahullaah- said:
“There is no doubt that the heart becomes covered with rust, just as metal dishes – silver, and their like – become rusty. So the rust of the heart is polished with dhikr, for dhikr polishes the heart until it becomes like a shiny mirror.
However, when dhikr is abandoned, the rust returns; and when it commences then the heart again begins to be cleansed. Thus the heart becoming rusty is due to two matters: (1) sins and (2) neglecting remembrance of Allaah. Likewise, it is cleansed and polished by two things : (1) istighfaar and (2) dhikr.”
Purifying ones heart is a constant and ongoing process that only stops when one enters the grave. Ibn Taymiyyah said:
“Verily, I constantly renew my Islam until this very day, as up to now, I do not consider myself to have ever been a good Muslim.”
[Narrated by Ibn al-Qayyim in ‘Madaarij as-Saalikin’ ; 1/218]
So turn to Allaah constantly. Ibn Al-Qayyim mentions:
“Verily the life of man is in the life of his heart and his soul.And there is no life in the heart except by knowing its creator,having love for Him,worshipping Him solely,turning to Him in times of need, and seeking tranquility with His remembrance.”