This is a very significant question which you inquired. Of course the point is that it is not too easy to reply to your question briefly. But briefly I can tell you that Satan(Shaitan) is the main reason that make such thoughts in our mind. In fact we can say that he the means for us that Allah can test us by this.

For instance you can read the text below (according to: http://www.islamquest.net/en/archive/question/fa1052  ) which shows three ways which Satan enters...  :

1. The beautification of ugly deeds: By making ugly actions appear beautiful, Satan effectively strips the otherwise inherent ugliness of sin and mitigates the societal taboo associated with sin in such a way that man easily falls into the trap of sin. This phenomenon can be witnessed in a person who rationalizes his wrong actions.

2. False promises: Through false promises and unattainable hopes, Satan renders man heedless of the Hereafter, death, and even Allah (awj). Such a person becomes a slave to his desires and is prepared to go to any lengths to attain the attainable, even if it means sinning against Allah (awj).

3. Fear: Satan scares man with thoughts of the future, compelling him to accumulate wealth, flee from jihad, aid the unjust, etc.

So I recommend you to read the following sites which are related to your question and actually could respond you.

www.islamquest.net

www.tebyan.net

This is a very significant question which you inquired. Of course, the point is that it is not too easy to reply to your question briefly. But briefly I can tell you that Satan  (Shaitan) is the main reason that make such thoughts in our mind. In fact we can say that he the means for us that Allah can test us by this.

For instance, you can read the text below (according to: www.islamquest.net) which shows three ways which Satan enters...:

1. The beautification of ugly deeds: By making ugly actions appear beautiful, Satan effectively strips the otherwise inherent ugliness of sin and mitigates the societal taboo associated with sin in such a way that man easily falls into the trap of sin. This phenomenon can be witnessed in a person who rationalizes his wrong actions.

2. False promises: Through false promises and unattainable hopes, Satan renders man heedless of the Hereafter, death, and even Allah (awj). Such a person becomes a slave to his desires and is prepared to go to any lengths to attain the attainable, even if it means sinning against Allah (awj).

3. Fear: Satan scares man with thoughts of the future, compelling him to accumulate wealth, flee from jihad, aid the unjust, etc.

So I recommend you to read the following sites which are related to your question and actually could respond you.

www.islamquest.net

www.tebyan.net

This is a very significant question which you inquired. Of course the point is that it is not too easy to reply to your question briefly. But briefly I can tell you that Satan(Shaitan) is the main reason that make such thoughts in our mind. In fact we can say that he the means for us that Allah can test us by this.

For instance you can read the text below (according to: http://www.islamquest.net/en/archive/question/fa1052 ) which shows three ways which Satan enters... :

1. The beautification of ugly deeds: By making ugly actions appear beautiful, Satan effectively strips the otherwise inherent ugliness of sin and mitigates the societal taboo associated with sin in such a way that man easily falls into the trap of sin. This phenomenon can be witnessed in a person who rationalizes his wrong actions.

2. False promises: Through false promises and unattainable hopes, Satan renders man heedless of the Hereafter, death, and even Allah (awj). Such a person becomes a slave to his desires and is prepared to go to any lengths to attain the attainable, even if it means sinning against Allah (awj).

3. Fear: Satan scares man with thoughts of the future, compelling him to accumulate wealth, flee from jihad, aid the unjust, etc.

So I recommend you to read the following sites which are related to your question and actually could respond you.

http://www.islamquest.net/en/archive/question/fa1052

http://www.tebyan.net/newindex.aspx?pid=220461

This is a very significant question which you inquired. Of course the point is that it is not too easy to reply to your question briefly. But briefly I can tell you that Satan(Shaitan) is the main reason that make such thoughts in our mind. In fact we can say that he the means for us that Allah can test us by this.

For instance you can read the text below (according to: http://www.islamquest.net/en/archive/question/fa1052 ) which shows three ways which Satan enters... :

1. The beautification of ugly deeds: By making ugly actions appear beautiful, Satan effectively strips the otherwise inherent ugliness of sin and mitigates the societal taboo associated with sin in such a way that man easily falls into the trap of sin. This phenomenon can be witnessed in a person who rationalizes his wrong actions.

2. False promises: Through false promises and unattainable hopes, Satan renders man heedless of the Hereafter, death, and even Allah (awj). Such a person becomes a slave to his desires and is prepared to go to any lengths to attain the attainable, even if it means sinning against Allah (awj).

3. Fear: Satan scares man with thoughts of the future, compelling him to accumulate wealth, flee from jihad, aid the unjust, etc.

So I recommend you to read the following sites which are related to your question and actually could respond you.

www.islamquest.net

www.tebyan.net