When you act natural, you will be in a better position to build relationships. Others will decide quickly if they feel comfortable around you. If they do, then they will be open to developing a relationship.
One problem with not being yourself is that it is difficult to maintain the false image. You may make mistakes and come in and out of your real personality.
As a result, this erratic behavior can be damaging to your relationships. It is best to always be yourself. The more that people trust you the more that they will want to do business with you.
Your personal brand is your networking identity. Do whatever you can to keep it in good standing.