Remember the rules for a healthy diet!
If you wish to feed yourself in a healthy way, you will most probably obtain the advice to use as much unprocessed and fresh products as possible. That maxim is valid for our spiritual alimentation, too.
Sermons about the NT may be compared to food that has undergone a (more or less elaborated) processing chain. Such processed food products may be easily consumed but they have lost (more or less) of their useful and healthy ingredients.
In the same way our spiritual health is being supported if we enjoy as much “food” as possible directly out of the Bible, i.e. if we read the NT on our own.