Parting from the ex-loved one is sometimes a real tragedy, especially if you are the weaker party, the one who earns less, who takes care of the children, who comes from a foreign country, etc.
If you are reading my article, the simplest, most obvious reason is that your marriage does not work! Whether it is your partner´s fault, yours, or the circumstances´, your relationship has suffered so much that perhaps it can no longer be healed.