Your personality type affects the way that you react to stress. There are three main stages.
When you have little or no stress, you find it easy to use the most appropriate behaviours for the situation. Very often, these are behaviours you may have learned at school, on training courses, etc.
As stress increases, 'learned behaviour' tends to give way to the natural style, so an ISTJ will behave more according to type when under greater stress. For example, in a crisis, you might find a place of solitude in which to think and work, collect more data/information, or use tried and trusted means of solving problems. However, you may also criticise others' efforts (when they, themselves, are under stress), and use pragmatic solutions at the expense of the long term.
Under extreme stress, fatigue or illness, the ISTJ's shadow may appear - a negative form of ENFP. Example characteristics are having a gloomy view of a future, suggesting impractical ideas, acting impulsively, and changing things without any thought. You might also have intense negative feelings towards others, though you might not necessarily express them. The shadow is part of the unconscious that is often visible to others, onto whom the shadow is projected. An ISTJ may therefore readily see these faults in others without recognising them in him/her self.
Next: ISTJ careers