Irrational desires offer no security: they can easily be gone the next day. Rational desires do: the fact that I can articulate the reason for their existence - trace them back to their root - means they are more likely to stick around.
Flipside: Justifying a goal hardens it. Even when my heart is not in it anymore, I still work towards the goal inertially, by telling myself the reasons why it was important to me.
cf. Minsky in Society of Mind: how can we set goals for ourselves years into the future?
This made me think about love: how can people put so much faith in their own feelings, to follow them and not think about whether that feeling will stay years into the future?
See also There are two types of truths in the world, Rumpelstiltskin principle, A Random Collection, and Aligning reason and feeling.