ISTJs main interest is to live in a secure and peaceful environment. Calm and reserved, they highly value loyalty, honesty and integrity. They respect laws and traditions: they will always try to do the right thing for their family and communities. ISTJs look generally serious but they can be a lot of fun – especially at family gatherings.
Extremely well-organized and methodical, they generally succeed at everything they undertake. They will work for long periods of time and use a lot of energy to accomplish any task as long as these tasks make sense to them or have a concrete application they understand. ISTJs have little use for theory and abstract thinking.
ISTJs are very hard workers who generally prefer to work alone but can also work well in the team if the situation demands it. They do not usually give themselves enough credit for their achievement because they just focus on fulfilling their obligations, which they consider as a duty. Because of their strong sense of duty, ISTJs can have a difficult time saying “no” when they are given more work than they can actually handle.
ISTJs are perfectionists and have a tendency to take other people’s effort for granted, just like they consider their own effort. As they are also likely to be uncomfortable expressing affection and emotion, they should remind themselves to compliment other people’s work from time to time.
This does not mean ISTJs are ungrateful. ISTJs are usually generous and care deeply about their family and friends. They are responsible parents and very good friends that will always act for the better good of others.
Note: I have done the Myers Briggs test of this before and was surprised, as I normally find I have a mixture of INFJ and INTJ, and find these twi personalities a lot more relatable than the one I received from this test.