Imam As-Sadiq (a.s.) said:
"صَلاحُ حالِ التَّعايُشِ و التَّعاشُرِ مِلء مِكْيال ثُلْثَاهُ فِطْنَةٌ وَ ثُلْثَهُ تَغافُلٌ"
Improving the situation of life and association is possible through using a measure, two thirds of which is vigilance and one third of which is negligence.1
No work project can be started without proper study, planning and vigilance, and yet a project cannot be completed in a timely manner without some bold decisions based on intuition, experience or outright risk-taking.
In other words, if we dive into endeavors without careful investigation, feasibility studies and work plans, we will not succeed. However, this should not mean that we get bogged down for months and years in trying to tie up all loose ends and going into unnecessary details to cover all possible uncertainties. In most cases, time is of essence for a successful outcome.
Hence the need to balance the vigilance for most part (two-third) with some non-vigilance or expediency (for the remaining one third).