Why should you give it up?

I'm starting this blog because I feel that as women there are few things that we take for granted when we are in a relationship. Most of us believe that once a guy says I love you, he must mean it. What if he doesn't mean it and he's in it for what he can get out of it. You can say the girl is equally in it for what she can get out of it. But why is it that she always the one that loses out when the relationship ends? It's simply because she's the one who has invested more or the one who has really been honest from the beginning.
So ladies if you're not sure about where the relationship is heading, why should you give it up? I heard recently heard that Steve Harvey wrote a book about waiting for 90 days before giving it up. That, to me, it's totally unacceptable. So what happens after 90 days? The guy will stick around after you've given it up, right?
Hey, guys are free to comment. And whatever you're saying you had better be ready to back it up