Ibn Kathir said:
“The believers, whom the human enemies kill, become martyrs, while those who fall victim to the inner enemy – Satan – become bandits. Further, the believers who are defeated by the apparent enemy – disbelievers – gain a reward, while those defeated by the inner enemy earn a sin and become misguided.” 
Reflection: Truly, the struggle against Shaytan and the self is among the greatest battles of man. A victory against his enemies might earn him some spoils of war, but a victory against Shaytan and his nafs (ego) will bring him closer to the spoils of the Hereafter. A brave fight against his enemies might earn him the favor of the general, but the struggle against his internal enemies will earn him the favor of the Lord of the Worlds. However, if he suffers a loss in this fight, he could very well lose his afterlife and earn the anger of his Lord from which there is no escape.
We can not allow ourselves to take any risks in this battle and we need every part of our body and mind to have the right attitude if we wish to succeed. If a part of us seeks this worldly life we should stop it in its track, with every means possible, lest we be exposed to danger like the muslim archers who left their position in the battle of Uhud, to seek the spoils, thereby exposing their army to the enemy. This fatal mistake resulted in 70 Companions being martyred, through which they earned the pleasure of their Lord. The consequences we might face, if any part of us show negligence, is much worse. The mistake of the archers earned 70 companions martyrdom and the pleasure of their Lord, but even a slip of our tongue could very well earn us 70 years in the hellfire and the wrath of our Lord. 
Some practical advice: You should know that if a person focus all his attention on warding off the Shaytan, while forgetting his own self which calls him to evil, he has made a big mistake. This is because his self is an even closer enemy than Shaytan and it is from the etiquette of Jihad to “Fight the ones who are close to you.” . So make sure that you constantly try to refine your character and discipline your ego when it shows sign of rebellion. An undisciplined army is not fit for battle and will not hold formation once the enemy launches his attack. Many of the Salaf would discipline themselves by fasting, night prayer and even denying themselves the permissible, in order to make their ego work for them and not against them. Ibn Jawzi advices:
“O you whose desirous self has subdued him, overpower your desires with the whip of endeavor and strong will, because when it becomes aware of your earnestness and seriousness of purpose it will surrender to your command. And, prevent it from enjoying what it desires from the lawful things, so that it agrees to abandon the unlawful.” 
Likewise, you should know that it is impossible to be consistent in ones victories against an enemy, if one does not know his enemy or himself. We we need to know how Shaytan misguides people, so we know how to protect ourselves. Likewise, we need to know our own strengths and weaknesses, and act accordingly if we wish to earn the assistance of the King and avoid temptation. The most obvious consequence of this understanding is that we stay away from places, actions and company, which we know will lead us into temptation. The importance of knowing oneself and the enemy has been pointed out by the Chinese general Sun Tzu, who wrote:
“If you know the enemy and know yourself, you need not fear the result of a hundred battles. If you know yourself but not the enemy, for every victory gained you will also suffer a defeat. If you know neither the enemy nor yourself, you will succumb in every battle.” 
 Tafsir ibn Kathir
 The Prophet(ﷺ) said: “A person may utter a word that he thinks harmless, but it results in his falling in Hellfire [the depth of ] 70 years [in travel]”, classified as hasan by al-Tirmidhi.
 At-Tawbah, (9:123)
 Ibn Jawzi, Kitab al-Lata’if fi al-Wa’iz (English translation: “Seeds of Admonishment and Reform”)
 Sun Tzu, “The Art of War” (as cited by goodreads.com). In case anyone is surprised I’m quoting a non-muslim on a islamic blog, I just wish to point out that such quotes can be found in the books of our scholars as well and as mentioned in a hadith, any word of wisdom is the property of the believer.