Have you been blindsided by a relationship that suddenly lost all its romance? Have you had great physical chemistry with a man that suddenly turned "ho hum" for no reason?

Why do relationships that have so much promise fizzle out and lose their spark?

There's a common mistake you might be making that will stop a great relationship in its tracks, before its even had time to grow. It's that once you know a man really likes you, you start to take his feelings for granted.

When a relationship is new and going well, it's a heady feeling. This is especially true if you've been dating a long time while looking for love. But the excitement of a new relationship can put stars in your eyes. It can give you a false sense of security, and you can find yourself thinking, "he likes me, he really likes me!"

As you begin to feel more confident and comfortable around him, you can unknowingly become more like his buddy than his girlfriend.

How do you know this is happening? It's when you begin to over-do and over-think things — all in the name of trying to make the relationship better.

Now that you "have" him, you start to push for things to be the way you want them and for what you believe should happen. In other words, you have an agenda for what you think the relationship should be.

You find yourself "shoulding" him a lot — when you should talk, when you should email and when you should text.

The more self-assured you become in the relationship, the easier it is to fall into the trap of taking charge. You've now become a friend, all the while convincing yourself that you're just "making plans."

Much of your control is driven by fear. If things don't happen the way you think they should, the relationship isn't what you thought — and it can't last. But remember: when you act out of fear you stop love in its tracks.

Most men don't respond well to control. For him things had been progressing in natural way, but now he's feeling the pressure of your "shoulds." He may not be able to put his finger on it, but his interest will cool. He'll find that being with you doesn't feel romantic anymore.

As your agenda grows, his interest will wane. At some point you'll reach a tipping point and love will evaporate.

From now on, try to channel the headiness of a new relationship by taking care of you. Enjoy the beginning and then let it be. When you do, you'll enjoy the pleasure of a long-lasting romance where you co-create an equal relationship and not one filled with one-sided "shoulds."