I have always considered myself a patient person, things that bothered the most of the people seemed to bother me as much. Traffic, rain, long queues, loud people. It was just part of life, why to grow hard feelings about those things.
It is easy to be patient when things are easy. All those things seemed easy for me, it is hard to be patient when things are hard and soon enough I have discovered my own version of hard. Pain.
Not psychological, real physical pain. Then the traffic and the queue have a different color, overstimulated me, finds it hard to quiet my mind and be compassionate with the person skipping the queue.
Next time I see someone impatiently moving I'll think twice, it might be this person is on pain.