Reason must guide the emotions, like a parent with a potentially unruly child. It is not that the child is bad, but when he becomes overactive, his behaviour can be destructive.
Reason encourages emotions to slow down when they begin to become overbearing.
Reason talks realistically to you about the trade-off of long-term happiness for feel-good now.
Reason points out that life never has been fair, so what?
The need for affirmation.