Reliability is important not only because accuracy and dependability are essential to creating (a book shelf, a relationship, or a new body), but because it allows us to take risks, try new methods, and dare greatly.
Knowing "old reliable" is available, provides a bit of comfort against the possibility that the new or innovative method doesn't quite work for you...yet. The reliable is your back up, your guard against Murphy's Law, a sign that you think forward and are prepared to thrive if things get slightly off track.
Reliability is essential, but should not be confused with validity. A bathroom scale may read 150 pounds each time you step on it. That indicates reliability. However, if you actually weigh 185, the reading is not valid.
In relationships, reliability is showing up when needed. It is being dependable. It is providing a consistent presence.
Of course that doesn't mean the relationship is valid.
Validating the relationship requires more than consistency. Validation requires trust, respect, and interaction.
Much like statistical reliability and validity, a relationship can be reliable yet not valid. However, it cannot be valid unless it is reliable.
In building your relationship with your students or teachers, being reliable is essential.