Honest and Direct - Integrity is the heart of the ISTJ personality type. Emotional manipulation, mind games and reassuring lies all run counter to ISTJs' preference for managing the reality of the situations they encounter with plain and simple honesty.
Strong-willed and Dutiful - ISTJs embody that integrity in their actions too, working hard and staying focused on their goals. Patient and determined, people with the ISTJ personality type meet their obligations, period.
Very Responsible - ISTJs' word is a promise, and a promise means everything. ISTJs would rather run themselves into the ground with extra days and lost sleep than fail to deliver the results they said they would. Loyalty is a strong sentiment for ISTJ personalities, and they fulfill their duties to the people and organizations they've committed themselves to.
Calm and Practical - None of their promises would mean much if ISTJs lost their tempers and broke down at every sign of hardship - they keep their feet on the ground and make clear, rational decisions. Peoples' preferences are a factor to consider in this process, and ISTJs work to make the best use of individual qualities, but these decisions are made with effectiveness in mind more so than empathy. The same applies to criticisms, for others and themselves.
Create and Enforce Order - The primary goal of any ISTJ is to be effective in what they've chosen to do, and they believe that this is accomplished best when everyone involved knows exactly what is going on and why. Unclear guidelines and people who break established rules undermine this effort, and are rarely tolerated by ISTJs. Structure and rules foster dependability; chaos creates unforeseen setbacks and missed deadlines.
Jacks-of-all-trades - Much like Analysts (NT), ISTJs are proud repositories of knowledge, though the emphasis is more on facts and statistics than concepts and underlying principles. This allows ISTJs to apply themselves to a variety of situations, picking up and applying new data and grasping the details of challenging situations as a matter of course.
Stubborn - The facts are the facts, and ISTJs tend to resist any new idea that isn't supported by them. This factual decision-making process also makes it difficult for people with the ISTJ personality type to accept that they were wrong about something - but anyone can miss a detail, even them.
Insensitive - While not intentionally harsh, ISTJs are often hurt more sensitive types' feelings by the simple mantra that honesty is the best policy. ISTJ personalities may take emotions into consideration, but really only so far as to determine the most effective way to say what needs to be said.
Always by the Book - ISTJs believe that things work best with clearly defined rules, but this makes them reluctant to bend those rules or try new things, even when the downside is minimal. Truly unstructured environments leave ISTJs all but paralyzed.
Judgmental - Opinions are opinions and facts are facts, and ISTJs are unlikely to respect people who disagree with those facts, or especially those who remain willfully ignorant of them.
Often Unreasonably Blame Themselves - All this can combine to make ISTJs believe they are the only ones who can see projects through reliably. As they load themselves with extra work and responsibilities, turning away good intentions and helpful ideas, ISTJs sooner or later hit a tipping point where they simply can't deliver. Since they've heaped the responsibility on themselves, ISTJs then believe the responsibility for failure is theirs alone to bear.