To my lover and my best friend....
I suspect the worst type of an intimate relationship is the type built on friendship; the type where the man and woman start out as BFF's then somehow evolve into intimacy/romance and all that. Friendship-based relationships seem more likely to devolve back into a friendship-based relationship - you've seen the type - where the husband and wife live as, essentially, roommates and pals with almost no real, deep connection. When a relationship starts out as merely friendship, I suspect in times of stress folks revert back to the baseline - friendship. I believe in times of stress - that's when intimacy, closeness, and all that is most-vital towards sustaining a couple. I'm still developing this thought, but that's what I think I think for now. Imagine breaking up with your spouse, and now you have no BFF with whom to counsel or talk or heal. Seems like insult added to injury. Further, might keep people in bad relationships because they may not have feelings for their mate, but they generally like their mate, as a person.
“… the greatest detractor from high performance is fear: fear that you are not prepared, fear that you are in over your head, fear that you are not worthy, and ultimately, fear of failure. If you can eliminate that fear—not through arrogance or just wishing difficulties away, but through hard work and preparation—you will put yourself in an incredibly powerful position to take on the challenges you face" - Pete Carroll.