love + happiness= sadness

When you meet your soul mate, it may not be everything you'd thought it'd be.  One would think that once you've met this person that most of your troubles would just fall to the way side but not the case, at least not here.
A man and woman meet, feel an instant connection and fall in love... the relationship builds, bonds are made but these bonds are not always easily maintained.
We live everyday lives, go about our business as if everything is great then a discovery is made...a rut has developed from within...things are suddenly not so clear, the feeling of love is still there but what has happened to the happiness that was once there? What has happened to the communication that is needed to keep things from getting to this point?  Too many questions, not enough answers and yet the questions keep coming.
Why would one not do everything possible before getting  to the point of no return? Why does love and happiness seem to turn to sadness without warning?