First, understand that the soul is made up of the will, mind, and emotions. Now you know that God wishes above all things that your soul is healthy (3 John 2 AMP). With these two things in mind also add that confessions of the past cleanses that soul with a renewed mind and making those old things to pass away (2 Corinthians 5:17 KJV).
As Christians we tend to say things with our emotions that seem to sound good but it actually isn't good at all. Let's recall being soooo in love to the point of this person being your whole world. You actually believed you were soul mates. Her eyes captivated your heart. Let's not forget the ever popular, you are my whole life. Saying these things didn't make the experience of being together anymore fulfilling. Those words only kept emotions ignited to the point of sexual temptation. Some held on until vows were spoken at the court house while others succombed to those vey words spoken. The sexual experience temporarily enhanced what was felt but eventually reality, which never left, cleared away all of those rose colored glasses that had been flung in the heat of passion. Jobs are still necessary. Bills still have to be paid. Laundry still needs to be done and "your whole world" would like to spend some alone time without you.
Stunned, you try to remain cool and agree just to keep the relationship together knowing that "alone time" means the sex wasn't altogether there, its going to be a slow breakup, exclusivity has not been established, maybe it was this or probably that - your mind is reeling. It doesn't take long yet that which you feared came upon you and it is over.
Though what I described was the demise of a relationship, this can also be a divorce, when someone passes away, or when the spouse is estranged and the waiting has been longer then expected. Those words that were spoken at the height of the relationship didn't disappear. You made that person your whole life and world. Your depression can be explained by what you have said. Your broken heart was made when you said that her eyes captivated it and now that the relationship is over, you will never see those eyes again. You imprisoned yourself with the words you spoke. Also if that estranged or insensitive person was your soul mate, what does that say about you? He/she left you destitute or without notice or didn't tell you and started dating someone else or sued you or evicted you out of the combined residence or called you out of your name, or stole money from you, or whatever that thing was. You connected your soul to that person soley from what you spoke and forgot about.
Alright let's make it as plain as it can be. God spoke and created all in 6 days, right? Greater is He that is in us, right? We learn to be more like Him by walking in love, right? Out of the abundance of the heart the mouth speaks, right? As a man thinks so is he, right? Can we not speak to the mountain to be removed? So what have you been allowing your emotions to say? Those words have staying power.
Repent, to allow those soul ties to be broken. New relationships aren't as vibrant and exciting not because of it being a rebound; its what was said. That soul mate is gone. That relationship is over. Your world (with that person) is over. Your life (as you thought it was) is over. Your heart cannot be captivated again; it is still imprisoned unless you confess, repent, and forgive. You don't ever let any person but Jesus be your whole life, world, or anything else. Nothing captivates you because Jesus came to set the captives free. To say otherwise is foolishness. Let Jesus be Lord of all having your heart and mind stayed on Him so peace can be obtained (Isaiah 26:3 KJV) and Kingdom Living can do what it does.