Great questions!

”One does not become enlightened by imagining figures of light but by making the darkness conscious.”
“Everything that irritates us about others can lead us to an understanding of ourselves.” – Jung

Relationships are the crucible in which we discover ourselves.

As you noted there is always push and pull in relationships as part of the purpose of relationships is to heal old wounds. Not only wounds created in the present but wounds that a person may have brought forward from childhood most of which are unconscious.

Your girlfriend general negativity in the morning is likely a play she created in which you play a role with the unconscious goal of healing. The role you play within that story will either confirm the fear behind the negativity or bring the fears into the light and healed. Sadly it is often true that due to our limitations that sometimes the pain of a relationship ending must be experienced in order to push someone to heal the past.

When we fall in love, this usually ushers in a special period, one with its own distinctive glow and magic. Glimpsing another person’s beauty and feeling, our heart opening in response provides a taste of absolute love, a pure blend of openness and warmth. This being-to-being connection reveals the pure gold at the heart of our nature, qualities like beauty, delight, awe, deep passion and kindness, generosity, tenderness, and joy.

Yet opening to another also flushes to the surface all kinds of conditioned patterns and obstacles that tend to shut this connection down: our deepest wounds, our grasping and desperation, our worst fears, our mistrust, our rawest emotional trigger points. As a relationship develops, we often find that we don’t have full access to the gold of our nature, for it remains embedded in the ore of our conditioned patterns. And so we continually fall from grace.
Intimate Relationship as a Spiritual Crucible – By John Welwood

Life which is love requires growth and becoming. Even a relationship where two people who have a great soul connection might have to end if the goals of two people point in different directions. That their calling/becoming might require the end of a relationship.

Have you ever asked yourself the question – What’s love got to do with it? You love someone, authentically, yet know that the relationships does not mean it should be one in which you remain together. Life which is love requires growth and becoming.

My observation has been that relationships are experienced multidimensionality – mind, body, and soul. We experience relationship in the day to day stuff of life, – taking out the garbage, cooking, cleaning, working… and then at a deeper level, spiritually, our senses of self and possibility… Both must be present for authentic relationship but more often than not we tend to pay attention to only one dimension and in doing so weight it too heavily. For example money troubles dominate and the spiritual sense of possibly we experience when we were with our partner is forgotten and neglected.

I was asked the other day what is the main attribute I look for a partner.
My answer is someone that does not panic when the love they experience in the various dimensions ebbs and flows.

Very much like the book ‘How to Be an Adult: A Handbook on Psychological and Spiritual Integration’ by David Richo