Stressed?

[C]hronic stress reduces cellular plasticity (including neurogenesis), which might make us (and mice) more likely to settle into familiar ruts and routines. The end result is that people stick with the very behaviors that created the stress in the first place.

Jonah Leher, Wired
See also: http://scienceblogs.com/cortex/2009/08/the_stress_spiral.php

That's why a change of scene is so powerful. Inner change of mental landscape with meditation. Outer change with travel.