OK, many years, side by side. Fun talk, fun times. Sometimes she confides in you, sometimes you in her. She cries, you lend a shoulder. That's a good thing.
Then you hook up. You have fun, she has fun. You're satisfied. She's in love. She will become dependent on you to continue that relationship. You're ok with that... for now.
Pretty soon she'll become more dependent, or vice versa. I'm thinking it will be her. Or she'll grow tired of you. You're not what she thought.
So you split up.
You're working side by side again. But it's quiet. Very quiet. And you pray that it will remain quiet. But it won't. Trust me, it won't.