Keeping an open mind and yet retaining your own ability for independent thought allows for growth and better understanding and conviction. There is a trend nowadays to view people who have logically and rationally analyzed "conventional wisdom" for themselves concluding in disagreement to some ideas that are popular as "narrow-minded" just because they do not jump on the proverbial bandwagon. Keep an open mind, but be logical and think out of the box. Some of the greatest leaders of countries have been those "who marched to the beat of a different drummer," who did not fall in line.
Keeping an open mind does allow for growth and change. Being a life-long learner, gathering information and adding to what we've previously learned, is good medicine for mental health. It's a big world and keeping an open mind will help us be better citizens of it.
I would agree with this, but I only really have one major point. If your mind is not open, you will not listen to any new ideas. If you do not listen to any ideas, you will never change from the way you are at this moment. If you do not change, how can you grow?