Imaam Ibnul Qayyim (rahimahullaah) said:
Disobedience is the cause being in shaytaan’s captivity and a prisoner of lowly desires. Among its afflictions is that a disobedient person is always in the captivity of his devil, the prison of his lusts and leadership of his desires; so he is a captive and a shackled prisoner. There is neither a captive whose state of affairs is more evil than a captive whose captor is his worst enemy, nor is there a prison more restricted than the prison of desires and shackles that are more restrictive than the shackles of lust; so how can a heart that is a captive and a shackled prisoner follow the path to Allaah and the home of the afterlife? How can he proceed upon a singular track when the heart is shackled and stricken with harm from every angle as result of the (severity) of its shackles? The likeness of the heart is that of a bird; it distances from harm whenever it flies high and surrounded by harm whenever it lands. It is reported in a hadeeth: ‘’Shaytaan is a wolf to a human being.’’ And just as an unprotected sheep in the midst of wolves is quickly destroyed, likewise if there is no protection from Allaah for the slave, it is a must that his wolf will prey on him.
He (i.e. the slave) is protected by Allaah through Taqwaah (fear of Allaah). It (Taqwaah) is a shield and shelter from Allaah between the person and his wolf; just as it is shield against punishment in this life and the afterlife. Whenever the sheep is closer to its shepherd, it is safer from the wolf and whenever it is distanced from the shepherd, it comes closer to being destroyed. So the sheep is more protected when it is closer to the shepherd, for the wolf only takes away the (sheep, cattle etc.) that are distanced and far away from the shepherd.
The basis of this affair is that whenever the heart is distanced from Allaah, then harm upon it is quicker, and whenever it is comes closer to Allaah, it is distanced from harm. Being distanced from Allaah is of various levels and some are more severe than others. Being distanced from (Allaah) through disobedience is greater than being distanced from (Allaah) through thoughtlessness; being distanced from (Allaah) through bidah is greater than being distanced from (Allaah) through disobedience, and being distanced from (Allaah) through hypocrisy and shirk is greater than all of that. [Source: Ad-Daa’u Wad-Dawaa’u’ page 119-120]