After carrying out any righteous action, one should feel within his heart that he did not carry out the action in the manner it ought to have been carried out. Similarly, one should have the fear that the action should not be rejected by Allah Ta‘ala.
In other words one should strive to the best of his ability to carry out the action in the most perfect manner. However, upon completing the action, one should be convinced that the action he had carried out is full of deficiencies and weaknesses, and thus it is certainly not in accordance to the majesty and grandeur of Allah Ta‘ala. Hence, he should fear that the action will not be rejected and flung at his face on the Day of Qiyaamah on account of the many deficiencies within it.
Thereafter, with this fear and remorse in his heart, he should cry to Allah Ta‘ala and beg Him to accept his action. He should also engage in istighfaar for his weaknesses.
(Malfoozaat Hazrat Moulana Muhammad Ilyaas (rahmatullahi ‘alaih) pg. 84)