Relationships are mirrors for us to learn more about ourselves. Relationships are mirrors of (1) who you were, (2) where you are now on your path and (3) your potential (who you know you are inside but have yet to manifest).
If an issue or person has an emotional "charge" to it, then you still have work to do. This mirror can feel challenging as it reflects the things you have not yet finished in your karma. These are matters we resist recognizing, accepting and integrating. Interacting with admired individuals gives you a glimpse at who you could be, if you let go of thoughts that hold you back.
All relationships exist so each human being can work on the spiritual self and karma. It is a process of polishing our own mirror. We do not see ourselves in the reflection and forget who we really are is beyond the mirror. The more you clear up emotional triggers/ issues, the more you discover you model the ‘right’ person, that person you tell yourself you are looking for in a partner or other relationship to feel whole.
Its helpful to remember every human is a spiritual being choosing to have a physical experience. That is, you are a soul in a body (for a while). Soul Mates are other souls that have agreed to connect with you on this planet for a purpose. In some cases it is to clear up karma, finish unfinished business, to achieve a particular goal together. When Soul Mates first meet they sense deja-vu. Every encounter is a pointer to what is beyond the mirror.