Excerpt from my numerology reading:
"You are also more vulnerable to astral attack than the other numbers simply because you are like a wide-open channel that is willing to receive psychic information from others. As some psychic information is destructive you need to learn meditation and psychic protection techniques to shield yourself from negative influences and energies."

Can someone tell me more about this ?

What includes psychic protection?

The astral level is mental.  So the mind must be trained, like any other muscle in the body, to be at its best and most effective.

Psychic abilities (which all of us have) are based upon our 5 senses and adding Intuition and I know (it neither sees nor hears - it just knows) onto the psychic sensitivities within the human construct.  This is available to us all and when we are interested in any topic (psychic included) it is important to gain knowledge as well as understanding.  A good teacher is a good start.

There are many paths to follow in psychic development...so much to choose from in the smorgasborg of life.  Choose wisely!

Grounding and Protection exercises are also different according to who you study with and ask.  A simple protection exercise to practice each morning and apply liberally during the stresses of your day:

Visualize a bubble (similar to one blown from a child's soap bubble pipe, complete with the rainbow patch - rainbows are such mystical/magical symbols of bridges, connections, communication and are complete with a pot of gold (prosperity) at the end) and see yourself completely enfolded within it.  It is filled with the white light of God's love and it will filter all negativity from within or without.