There is no guarantee that a strong person will live long or a weak person will die soon. There is no guarantee that an educated person will be successful or an uneducated person will be a failure. There is no guarantee that a pious person will not become sinner or an impious person will not become a saint. There is no guarantee that a rich man's son will not become poor or a poor man's son will not become rich. There is no guarantee that one who joined the race early will be the first to finish it or one who joined late will be last to finish it.
Life is such that nothing is guaranteed - everything is predictably unpredictable. God's plan and logic will defy all our logic and short-circuit it. If He wishes, He can make a plum into an apple or an apple into a plum. If He wishes, He can make a King into a pauper or a pauper into a King. God's ways of working are inconceivable. We are always subordinate to His wishes. That's why, whenever any disciple of Bhakti Siddhanta Saraswati (a great Vaishnava reformer) asked him about his plans. He would invariably answer - "If Krishna so desires then I will do so and so." He knew that ultimately only His wish prevails. We also should add the words, "If He so desires" in our language and in our thoughts.
In conclusion, we need to be always humble and never arrogant about "who we are" and "what we have" while being completely nonjudgmental about "who others are" and "what they have" for if He wishes things can change in a moment.