Imam Bagher (P.B.U.H) – the fifth leader after the Prophet Muhammad- says:
Three things demolish man: one who magnifies his good deed, and one who forgets his sins, and one who is opinionated.
Brief description:
those who magnify their deeds, surely are satisfied with that, and this attitude hinders them from progress and development.
and those who forget their sins, everyday are stained with a new sin instead of compensating their previous sins and will fall down suddenly.
and those who rely only on their own opinion, are deprived from the support of public thoughts and abundant minds and knowledge of others. they are repeatedly involved in mistakes, and finally their back will break under the mass of problems.
vasael-ul-shia, volume 1, page 73
قال رسول الله صل الله علیه و آله
ثَلثُ قَاصِماتُ الظَّهْرِ: رَجُلٌ إسْتَكْثَرَ عَمَلَهُ وَ نَسِىَ ذُنُوبَهُ وَ أَعْجَبَ بِرَأيِهِ
سه چیز پشت انسان را می شکند: کسی که کارهای نیکش را بزرگ کند، کسی که گناهانش را فراموش کند، و شخصی که خود رأی و مستبد باشد