Deviation from the correct creed
The correct creed is compulsory to protect Deen (Islam). If the correct tenets have not been achieved and inculcated, there is high apprehension of deviation and getting out from the fold of Imaan and Islam. This is the most threatening way to easily and completely lose Imaan! At present, there are many people who practice good actions like saying prayers on a regular basis, but by denying an established rule by the Quran and Sunnah, they deviate. There are people who mock the people of knowledge and the righteous (especially because of their good actions). Such acts ultimately bring the mockers out from the fold of Islam. There are people who rigidly or arrogantly believe that interest, lies, and any such evil actions are/should be made halaal today. They also get out from the fold of Islam. By not knowing the compulsory fundamental knowledge of Islam, people deviate and go astray completely.
Aversion and negligence toward the acquisition of Ilm, i.e., divine knowledge
Aversion to seeking useful knowledge creates confusion in the heart of man. The ideas and beliefs that people cherish have a direct impact on their actions. Therefore, people stray from the knowledge of the Quran and Sunnah. This leads to deviation from the correct creed, hatred to the people of knowledge, and getting engaged in major sins uncaringly. There are also people who acquire divine knowledge, but fully through the way they desire to. This is another dangerous path because this leads to unauthorized self-satisfaction that is completely a wrong way and methodology to earn and practice divine knowledge and good actions.
Ignoring, opposing, or neglecting the development of etiquette
A very ignored quality today — not only in the masses but also in the people who somehow keep a strong bond with the pious and knowledgeable. Many people are known as pious, learned, and they possess many exceptional qualities; however, etiquette and humility seem completely absent in their life! Basically, politeness, humility, modesty, obedience are a prerequisite for being pious. Acquisition of the right creed and Ilm, and even after practicing upon good deeds on a regular basis, those who are not humble and obedient in manners become rude and deviate from the righteous path.
To entertain confusions and no steps taken to redress
Many people fall into various confusions by others or by themselves. Thereafter, various poisons enter their thoughts, consciousness, and actions. They do not discuss these with any qualified person, nor do they take any steps to think of any treatment to get rid of it/those. Many people do take some advice or consult but do not take the corrective actions (advice/way out/warnings) prescribed by the seniors. Inaccurate and impure thoughts and actions lead people to various kinds of confusion. At one point, the individual is reluctant to accept many truths naturally, overpowered by his own ideas. Thus he goes astray through confusing thoughts and deeds. Such is the condition of sinners who may possess vast knowledge and also their followers.
Intense laziness and reluctance toward good actions
Many people neglect good deeds, especially the obligatory ones. Gradually they occupy in useless actions, a large amount of waste of time, and get engaged in sins as well. The common nature of such people is to lag behind with lame excuses. They procrastinate and never reach their destination!
Develop/nurturing excessive worldly love
The type and amount of worldly love may vary from person to person. Excessive love for this world and worldly possessions absorb the heart in earning and doing more for the temporary, giving precedence over the afterlife. There is a limit to get engaged in worldly affairs. It is important and also commendable up to a certain limit level. But the consequences of being too busy and too ambitious for this world and its possessions make man oblivion of his accountability to Allah and slowly pushes someone away from the right path.
Delaying repentance by committing sins
Not repenting after committing sins or neglecting and making delays in repentance turn people away from the truth, righteousness, honesty, and all goodness. Through this way, many deviate from the right path, may become frustrated, disappointed, and depressed. The consequences of this condition ruin one’s morality and obligations to Allah and His servants. This is another way, a large number of people who born as Muslim but finally deviates from Islam.