“You must worship no other gods, for the Lord, whose very name is Jealous, is a God who is jealous about his relationship with you” (Exodus 34:14, NLT).
Jealousy is viewed as a negative trait and with good reason. The green-eyed monster can lead to suspicion, arguments, violence and even murder. A first glance at this verse doesn’t make God sound too good. It brings to mind stories of the Greek and Roman gods, with their petty jealousies and rivalries. I haven’t said it in a long time—God isn’t like us! And his jealousy doesn’t resemble ours in any way, shape or form.
God is jealous in a good way. This article gives a good (and fairly lengthy) explanation of this term as it applies to him. I especially love this: God is “eager about protecting what is precious to him.” He isn’t green-eyed, petulant and childish about our relationship. He doesn’t pout when our affections wander away from him. He is caring, concerned and protective and knows what is best for us. We really are like children in many ways and we are so precious to him that when we hurt, he hurts. Being jealous over us is a positive aspect of his deep and unending love.
Jesus - Son, Savior, God 
It is all about attitude – that is why the definition of love in 1 Corinthians 13