Psychic protection is about protecting yourself from ghosts and spirits so you don't have to channel them. It is entirely possible that you will feel drained or affected by them, but that doesn't mean that they are bad spirits. There are, of course, earthbound spirits as well. These spirits will attach themselves to your aura and they will drain your energy and your aura and they will victimize you as well. These spirits aren't bad; they are just stuck so it is important to know how to protect yourself from them if you want to make any progress.
One of the best ways for you to raise your vibration so you can detect spirits more would be to include the Divine. This means that you call upon God, or an Archangel such as Raphael or Gabriel and you position yourself in a state of awareness. Another way to protect yourself would be to be more selective about who you channel. After all, you don't want to open yourself up to anyone, because you want to channel your spirit guides or your guardian angels. If you are channelling and you don't know who is coming, you can find someone who will teach you and this is a great way for you to know whether or not you are making the right decision. Empaths need psychic protection the most. An Empath is someone who has the ability to explore what it is like to be another person. They are very effective at doing this and they can often come back with unwanted feelings from another person's experience as well.
Psychic shields are like bandages. Sometimes they work, and when they do it is only a temporary measure. After all, you want to have control over your own psychic and you don't want to rely on someone else to do it for you, so keep this in mind.