Emotion is a good element in yoga; but emotional desire becomes easily a cause of perturbation and an obstacle.
Turn your emotions towards the Divine, aspire for their purification; they will then become a help on the way and no longer a cause of suffering.
Not to kill emotion, but to turn it towards the Divine is the right way of the yoga.
But it must become pure, founded upon spiritual peace and joy, capable of being transmuted into Ananda. Equality and calm in the mind and vital parts, an intense psychic emotion in the heart can perfectly go together.
Awake by your aspiration the psychic fire in the heart that burns steadily towards the Divine—that is the one way to liberate and fulfil the emotional nature.
Ref : Letters on Yoga Vol. II