"Set me as a seal upon thine heart, as a seal upon thine arm: for love is strong as death; jealousy is cruel as the grave: the coals thereof are coals of fire, which hath a most vehement flame." (Song of Solomon 8:6, emphasis mine) "[They] that sweareth to [their] own hurt, and changeth not." (Psalm 15:4b)
Well put. If we're honest with ourselves--and honest in general--we know we're made for one person. There's all sorts of places to go with this but that one person. That one person for whom we'd give our all, to whom we'd give our heart and strength and life. Under God, I believe that we're made for one and only one and this is what gives rise to jealousy. And the jealousy described in the above sounds about as poetic as one could wax on the subject.
But we change too, don't we? This is a fact of life. Granted: "Jesus Christ the same yesterday, and to day, and for ever." (Hebrews 13:8) But we're turning more and more into the likeness that is both based on Him and also the originality with which He planted in us when He made us. Praise God. Waiting on God to make Him into who we are and also for us to be comfortable in that (two different things) is what will kill the wrong kind of jealousy. If you're looking to someone else--whoever it may be--to complete you without first realizing you're already "complete in Him" (Colossians 2:10), you're gonna have a bad time down the road. Because you'll change and something deep may fracture and that's not good. Doesn't mean God can't heal it and that it can't in turn be stronger than before. But you could circumnavigate all that by waiting. It's hard and it might hurt (a lot), don't let anyone tell you different.
"I am the Lord: that is my name: and my glory will I not give to another, neither my praise to graven images." (Isaiah 42:8)
"Howbeit then, when ye knew not God, ye did service unto them which by nature are no gods." (Galatians 4:8)
So that word in Hebrew translated "vehement flame" is shalhebeth. A "flare" (Strong's). You can understand how one of the names of God would be "El Qanna"--the jealous one. Because He has a heart only for you. This is why the Israelites were spoken of as having gone "a whoring" after other gods. God takes very seriously the time and effort and attention (all love) that has gone into preparing the way for us.