Fear of the unknown
For it is not inertia alone that is responsible for human relationships repeating themselves from case to case, indescribably monotonous and unrenewed: it is shyness before any sort of new, unforeseeable experience with which one does not think oneself able to cope.Indeed.
We, however, are not prisoners. No traps or snares are set about us, and there is nothing which should intimidate or worry us... We have no reason to mistrust our world, for it is not against us.
- Rainer Maria Rilke, "Fear of the Inexplicable"