trust???

if you gaze for long into an abyss,
the abyss gazes also into you.

-Friedrich Nietzsche

i find this quote fascinating. i tend to try and see peoples reasoning behind what they do to the point of perhaps exposing my own vulnerabilities to them.
people are very interesting to me. trusting a mere human with that which causes you the most pain is kinda foolish if you think about it.
who can we truly trust and can we trust them forever or only for as long as we are in their good graces?