ISTPs can be very intense and exciting individuals. Their strong Thinking preference makes them seem rather aloof and "hard to get". Their Sensing and Perceiving preferences make them sensual, earthy individuals. These attributes frequently make them attractive to the opposite sex. ISTPs live entirely in the current moment, which makes them especially interested in new sensations and experiences. They strongly dislike routine and strict schedules, and resist being controlled by others. They are fiercely independent and need their own space within a relationship. When involved in relationships which provide for their basic needs and which present them with new experiences, the ISTP will be happy to do what's necessary to keep the relationship alive and well. If a relationship becomes boring or oppressive to the ISTP, they will try to fix it, or move on. ISTPs take their commitments on a day-by-day basis. Even if they say "I do", it usually means "I do for now". They do not like to make lifelong commitments, although they may very well be involved in lifelong relationships which they have taken one day at a time.
Sexually, the ISTP approaches intimacy as a physical act rather than an expression of love and affection. They are earthy and sensual beings who enthusiastically experience sex with all five senses. They bring spontaneity, creativity, and enthusiasm into the bedroom, and enjoy new experiences. Since aesthetic beauty has such strong appeal to them, they appreciate the "setting", i.e. bedding, lingerie, cologne, etc.
ISTPs love to fix things, and may create problems in their personal relationships, just so that they can have the fun of fixing them.
They have a tendency to hold back their own views on things. They like to listen to other people's views, but are generally non-commital about expressing their own opinions. ISTPs have a habit of evading answering questions by asking more questions. This can be frustrating at times to their mates, if they are after a direct answer. The ISTP's decision making process is entirely internal, so they don't feel much need to share their opinions with others. When they are interacting with others, they are in "information gathering" mode, so they tend to ask questions rather than share views. The ISTP just doesn't feel the need to expose themselves fully to others. When it comes to intimate relationships, the ISTP has the further motivation of protecting themselves. Most ISTPs are afraid of having to deal with their deeper feelings. Since their Thinking preference dominates their personality, their Feeling side is their least developed (inferior) function. Consequently, ISTPs are usually quite vulnerable and perhaps weak when dealing with their feelings. Their habit of keeping part of themselves hidden may also serve the purpose of keeping a protective wall around their hearts.
Although the ISTP does not usually have a well-developed Feeling side, they frequently do have intense feelings for people. They can feel overpowering love for their mates, although they are likely not to express their emotions, or to express them inadequately or inappropriately if they do venture towards expression. However, unlike many of the other personality types, ISTPs feel strong affections one day at a time. One day, they may feel completely, intensely in love with their mate, and the next day they may be totally disinterested, or perhaps even ready to move on. This "live for the moment" type of approach is different from how most other types experience their feelings, and is difficult for many to understand. Consequently, the ISTP may be called "fickle" or "cold". In fact, they are not really fickle, and certainly not cold. They simply experience their lives on a moment by moment basis, and go along with it's natural flow. However, since most people need more commitment than can be offered when taking things day-by-day, the ISTP who wants to remain in a relationship will have to resolve themself towards being involved in a more traditional commitment.
For most ISTPs, making a commitment to an intimate relationship will require an effort to stretch themselves outside of their comfort zones. However, those who do so will realize that they can enjoy the benefits of a strong, committed relationship and still live their lives in the present tense.