You cannot get something new if you are holding on to something old with a tight fist.  Likewise, it is good to have a mind that is open to new ideas.  We are not saying that you should disregard anything or any thought that is old, just because it is old.  Nor are we saying that anything or any thought that is new should be embraced.  Rather, everything should be approached with an open and critical mind so that you can let go of things and thoughts that no longer serve you, and welcome new things and thoughts into your life.  Dare to let go of the fear of the unknown, and to be open.