Welcome to the site. Please know it is not a habit, it is an addiction, big difference there and you have to realize that.
Read all you can, stay away from those friends who dip. There are many, many of us that wish we would have done this in college also. You are a smart guy for quitting....your friends will try and get you to dip again becaues they will see themselves as weak and it will make them feel better if they see you being weak also...don't do it. Stay strong, we are here for you.