There are ten useless matters:
Knowledge that is not acted on
The deed that has neither sincerity nor is based on following the righteous examples of others
Money that is hoarded, as the owner neither enjoys it during this life nor obtains any reward for it in the Hereafter
The heart that is empty of love and longing for Allah, and of seeking closeness to Him
A body that does not obey and serve Allah
Loving Allah without following His orders or seeking His pleasure
Time that is not spent in expiating sins or seizing opportunities to do good
A mind that thinks about useless matters
Serving those who do not bring you close to Allah, nor benefit you in your life
Hoping and fearing whoever is under the authority of Allah and in His hand; while he cannot bring any benefit or harm to himself, nor death, nor life; nor can he resurrect himself.
However the greater of these matters are wasting the heart and wasting time. Wasting the heart is done by preferring this worldly life over the Hereafter, and wasting time is done by having incessant hope. Destruction occurs by following one’s desires and having incessant hope, while all goodness is found in following the right path and preparing oneself to meet Allah.
How strange it is that when a servant of Allah has a [worldly] problem, he seeks help of Allah, but he never asks Allah to cure his heart before it dies of ignorance, neglect, fulfilling one’s desires and being involved in innovations. Indeed, when the heart dies, he will never feel the significance or impact of his sins.
Imam Ibn ul Qayyim al Jawziyyah