Some of us growing up had it quite easy, and some of us not so much. We're not blaming our parents, because they loved us and did the best with whatever they had. But even if we had it easy, life does its thing and there could have been a divorce, lack of money, or illness.
So we all developed ways to cope, and that's a good thing because it helped us grow-up and do life. But, what we don't realize when we meet our partner is that they're actually a composite of the positive and negative characteristics of our caretakers or parents.
The term "Imago" means image, and it means we have a picture somewhere in our unconscious mind of what love is supposed to look like, sound like and feel like - that's what creates the buzz of romantic love. That's why people say things like "I feel like I've known you all my life", or, "You feel so familiar" or "I feel like I've found my home." Because, in a way, you've actually found your home.
However, after a certain point, your partner is going to do something that's reminiscent of your most vulnerable, difficult, or disappointing moments. But, that's actually what's supposed to happen. If you understand that life is about growing and healing, then it makes sense that you'd pick someone who is going to trigger you, and give you the opportunity to grow up and to heal.