Economics of Relationship

I once heard from a prof in college (from Econ to be specific) that Love or Marriage is like a business. You must choose someone who will give benefits to you.
I thought it was a piece of crap. I was 19 then. When i was at the verge of teen and young adult age, i still believe in fantasies. I did consider having that invisible magic before jumping into a relationship.
I think when you reach the age of 23, that’s when you start thinking about your future. You get to review all the relationships you have, and think carefully which one to ditch.. it  is the one you won’t get business from and you’d get debits intead. it is the least you want in your life.  
And that is the major dillema im going through right now. I am thinking and reviewing critically all what I have. Should I just rely on what future holds? but i am afraid i am risking all that i might have here.. Or better yet, should i act the principles of practicality..?
I am just making my life miserable.. contemplating what is not served yet.
This is an emotional stage and i am afraid that i am losing someone..
i must think deeper and decide later..