The subconscious works in many ways and dreams are generally signifiers for things metaphorically.
The fact you are breaking up with someone is a signifier for completing something. If you have completed something in your life or have finished with a task or trial this may be just a signifier for it.
The dream may also mean that you and your partner have left behind something in your relationship and are breaking away from it. This may be a subconscious realisation on your part which is only manifesting itself in your dream.
If for example, you broke up with your ex in real life and the dream saw you break up with your current partner and get back with your ex, this is just your mind speculating.
Our minds do this to see how we feel about things by playing them out mentally so we can gauge what it actually is that we want.
The dream may also mean you have to work on your relationship. The best thing to do is to write down future dreams and purchase a dream interpretation book. Here you can write down and compare what your dreams mean to the book.
The best way for a healthy mind is meditation, healthy wholesome food and physical exercise. These three things will lead to balanced better decisions and easier understanding of your dreams.