According to Meyers-Briggs, I'm an ISFJ...
ISFJs live in a world that is concrete and kind. They are truly warm and kind-hearted, and want to believe the best of people. They value harmony and cooperation, and are likely to be very sensitive to other people's feelings. People value the ISFJ for their consideration and awareness, and their ability to bring out the best in others by their firm desire to believe the best.
ISFJs have a rich inner world that is not usually obvious to observers. They constantly take in information about people and situations that is personally important to them, and store it away. This tremendous store of information is usually startlingly accurate, because the ISFJ has an exceptional memory about things that are important to their value systems. It would not be uncommon for the ISFJ to remember a particular facial expression or conversation in precise detail years after the event occured, if the situation made an impression on the ISFJ.
More so than other types, ISFJs are extremely aware of their own internal feelings, as well as other people's feelings. They do not usually express their own feelings, keeping things inside. If they are negative feelings, they may build up inside the ISFJ until they turn into firm judgments against individuals which are difficult to unseed, once set. Many ISFJs learn to express themselves, and find outlets for their powerful emotions.
Just as the ISFJ is not likely to express their feelings, they are also not likely to let on that they know how others are feeling. However, they will speak up when they feel another individual really needs help, and in such cases they can truly help others become aware of their feelings.
The ISFJ feels a strong sense of responsibility and duty. They take their responsibilities very seriously, and can be counted on to follow through. For this reason, people naturally tend to rely on them. The ISFJ has a difficult time saying "no" when asked to do something, and may become over-burdened. In such cases, the ISFJ does not usually express their difficulties to others, because they intensely dislike conflict, and because they tend to place other people's needs over their own. The ISFJ needs to learn to identify, value, and express their own needs, if they wish to avoid becoming over-worked and taken for granted.
ISFJs need positive feedback from others. In the absence of positive feedback, or in the face of criticism, the ISFJ gets discouraged, and may even become depressed. When down on themselves or under great stress, the ISFJ begins to imagine all of the things that might go critically wrong in their life. They have strong feelings of inadequacy, and become convinced that "everything is all wrong", or "I can't do anything right".
The ISFJ is warm, generous, and dependable. They have many special gifts to offer, in their sensitivity to others, and their strong ability to keep things running smoothly. They need to remember to not be overly critical of themselves, and to give themselves some of the warmth and love which they freely dispense to others.