Unpredictability of good and bad things in life.

Good and bad things happen in our life when we least expect them. There is an in built unpredictability about the timing of such events. If anyone desires to find an answer, well Mahabharatha gives a good explanation.
नापदामस्ति मर्यादा न निमित्तं नकारणं
धर्मस्तु विभाजत्यार्थम उभयो: पुण्य पापायो:
(There is no limit for dangers। It can occur at any time and that too without reason.Yama evaluates all the good and bad deeds done by us and gives its consequences at the time he thinks suitable.)
Well, my colleague Rajesh tolerated my penchant for shlokas during our stay elsewhere on a certain mission. He was gracious in acknowledging the above shloka as very true. I am sure, you too will like it.