In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam Ibnul Jawzi [rahimahullaah] said:
At-Talbees – Deception – is to show falsehood in the image of truth. Ghuroor – being misled – is a type of ignorance that necessitate believing that something corrupt is correct, and that something bad is good. Its cause is due to the presence of doubtful matters, rather Iblees sways people as much as possible and increases his ability from them. This becomes lesser depending on the level of their vigilance, heedlessness, ignorance and knowledge.
Know that the heart is similar to a fortress, fences surround this fortress and have doors. The fortress [i.e. the heart] has fissures and the intellect resides inside it. The angels frequent the fortress and on its side there is a stable that contains desires; the devils go to that stable in turns without obstacle, a war is established between the people of the fortress and the people of the stable, and the devils do not cease going around the fortress seeking for the opportunity when the guard becomes heedless or to go through the fissures. Therefore, the guard must know all the doors of the fortress that have been placed under his responsibility and all the fissures lest he drops his guard for even a moment because the enemy never drops his guard. The fortress is brightened with remembrance of Allaah and radiant with Eemaan, and there is a bright mirror in there that reveals the images of everything that goes past; so the first thing the devils do in the stable is that they increase the smoke, so the walls of the fortress become darkened and the mirror becomes rusty; however perfect remembrance of Allaah repels the smoke and the glaze of the Dhikr cleans the mirror.
The enemy carries out attacks against the fortress, so sometimes he tries and enters the fortress, but the guard charges toward him and he exits. And it maybe that he enters to cause havoc and stays in due to the guard’s heedlessness. And it may be that the wind that repulses the smoke settles down, so the walls of the fortress become darkened and the mirror becomes rusty, then the devil goes past and none knows about it. And it maybe that he injures the guard due to his heedlessness, imprisons him, utilises him for his service, establishes himself, devise tricks to seek an agreement with the person’s evil desires and to agree with him, and may become as if he is a man with understanding but upon evil. The most robust chain by way of which captives are shackled is ignorance, the one of medium strength is evil desires and the weakest one is heedlessness. As long as the armour of Eemaan is on the believer, then indeed the arrows of the enemy will not land on the vulnerable places that will lead to death.
Abu Ghassaan An-Nahdee [rahimahullaah] said, “I heard Al-Hasan Bin Saaleh [rahimahullaah] saying: ‘Shaytaan opens ninety nine doors of good for the servant whilst desiring to open one door of evil’”. Hammaad Bin Shuaib [rahimahullaah] narrated from Al-A’mash [rahimahullaah] who said, “A man who used to speak to the Jinn narrated to me that they say, “There is none more difficult on us than the one who followers the Sunnah, but as for the people of desires [i.e. ahlul bidah], we play with them without trouble’”. [Ref 1]
Imaam Ibnul Qayyim [rahimahullaah] said: Disobedience is the cause of being in shaytaan’s captivity and a prisoner of lowly desires. A disobedient person is always in the captivity of his devil, the prison of his lusts and leadership of his desires. He is a captive and a shackled prisoner. There is neither a captive whose state of affairs is more evil than that of 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 follow a single path when the heart is shackled and stricken with harm from every angle as a 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 inevitable that his wolf will prey on him.
He is protected by Allaah through Taqwaah. Taqwaah is a shield and shelter from Allaah between the person and his wolf; just as it is a 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] 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. 
Imaam Ibnul Qayyim [reahimahullaah] said:
قَالَ فَبِمَا أَغْوَيْتَنِي لَأَقْعُدَنَّ لَهُمْ صِرَاطَكَ الْمُسْتَقِيمَ
ثُمَّ لَآتِيَنَّهُم مِّن بَيْنِ أَيْدِيهِمْ وَمِنْ خَلْفِهِمْ وَعَنْ أَيْمَانِهِمْ وَعَن شَمَائِلِهِمْ ۖ وَلَا تَجِدُ أَكْثَرَهُمْ شَاكِرِينَ
(Iblis) said: “Because You have sent me astray, surely I will sit in wait against them (human beings) on Your Straight Path. Then I will come to them from before them and behind them, from their right and from their left, and You will not find most of them as thankful ones (i.e. they will not be dutiful to You).” [7:16-17]
[ثُمَّ لَآتِيَنَّهُم مِّن بَيْنِ أَيْدِيهِمْ – Then I will come to them from before them and behind them]; Ibn Abbaas (radiyallaahu-anhumaa) said this means, ‘’I (Iblees) will bring doubts to them about the Hereafter.’’ [وَمِنْ خَلْفِهِمْ – and behind them]; Ibn Abbaas (radiyallaahu-anhumaa) said that this means, ‘’I (Iblees) will make them covetous for the worldly things.’’ [وَعَنْ أَيْمَانِهِمْ – and from their right]; Ibn Abbaas (radiyallaahu-anhumaa) said this means, ‘’I (Iblees) will make their religion obscure (in the sense that they will hold onto doubtful matters which they would consider to be the truth). [وَعَن شَمَائِلِهِمْ – and from their left]; Al-Hasan (rahimahullaah) said this means, ‘’I (Iblees) will command them to commit evil deeds, urge them toward it and beautify it in their eyes (i.e. make it fair seeming to them).’’ It has also been reported from Ibn Abbaas (radiyallaahu-anhumaa) who said that Iblees did not say ‘’And from above them’’ because he knows that Allaah is above them. Qataadah (rahimahullaah) said, ‘’O son of Adam! Shaytaan comes to you from every direction but not from above because he is not able to come between you and the Mercy of Allaah. 
[Ref 1: An Excerpt from Talbees Iblees’ with the checking of Shaikh Zayd Bin Haadee (rahimahullaah). Pages 42-43. Slightly paraphrased]
[Ref 2: An Excerpt from ‘Ad-Daa’u Wad-Dawaa’u’ page 119-120’. slightly paraphrased]
[Ref 3: An Excerpt from ‘Badaai at-Tafseer al-Jaami Limaa Fassarahu Al-Imaam Ibnul Qayyim’ Vol pages 377-379]