Factors that lead to the weakening of Istiqamah

• Committing sins (ma'siah), insisting on repeating them again and again, without istighfar (seeking Allah's forgiveness) and without practicing repentance.
  
• Shirk (associating anything with Allah) whether in intentions, by showing off our good deeds to others, seeking others' appraisal, avoiding being blamed by others, being afraid of someone, or to seek rewards from others than Allah. This part of shirk is also called riyya' or showing off. All these lead to deviation in Istiqamah, and when these stimuli are not there, the person's work is not perfect any more and it is not done in the best way possible.
  
• Nifaq (hypocrisy). There are two forms of nifaq: in belief and in action. The Muslim who surrenders totally to the will of Allah and accept Islam based on his/her choice is free from the first form of hypocrisy. However any Muslim is subject to and should avoid the second form of nifaq which the Prophet, sallallahu 'alayhi wasallam, warned us about: Not keeping promises and breaking them continuously without good reasons or excuses, not fulfilling commitments we make with others, being aggressive and unjust to others in quarrels, and disputes, failing to shoulder responsibilities/burdens we are entrusted with, etc. All these bad qualities should be avoided since they lead to the weakening of our Istiqamah.
  
• Bida'ah (innovations in ibadah), whether genuine bida'ah (performing ibadah which has not been ascribed by Shariah, i.e. revelation), or relative bida'ah (failing to observe the requirements of doing ibadah - the five criteria discussed in Hadith 5), will lead to decreasing the quality of good action or ibadah.
  

There are other factors that also contribute to the weakening of Istiqamah, such as: recklessness, reluctance, heedlessness, being overwhelmed by a deceiving enjoyment, and being mislead by self interests and desires