My apologies for evading the OP Smile "Entities attack, can you really be harmed by the astral entities?"
During my first few months of serious OB practice I was more ignorant than aware of any harm that may occur during OB because in those days there was no internet telling all the fiction stories and sheer non-sense you can read about in abundance today. The facts of the matter are as simple as it may appears incorrect to those who have been believing these stories.
I am going to try to explain this as simply as possible and so please forgive me if it may not be as detailed as you may want it to be, this is a complicated affair...but we can go more into areas if needed.
We are Beings who, at this point in our consciousness journey, require 'other' bodies or vehicles of expression to sense and realise our surroundings... in the Physical world we have a body, which has absolutely no ties to us as Beings, we use it to sense and experience the physical world... when out of the physical body we have a Causal Envelope, which is the vehicle in which we reside. This Causal Envelope will also one day be discarded when we move from the human kingdom to the next higher or 5th kingdom of life... when we are then no longer human.
Now this Causal Envelope is an extremely powerful and resilient 'covering' which protects us as 'young' Beings during out of body times...and remember we all leave our bodies every single time we sleep deeply, and no one really comes back with a black eye, unless your body fell out of bed Smile
There are many 'entities' in the higher worlds, but the word 'entities' is misleading because it cungers up all kinds of scary thoughts. These Beings who reside in various levels of the higher worlds belong there just as you and I belong in the physical world right now, and I have never ever had anything that even resembles an attack from any of them. The most terrifying thing is encountering them for the first time might be a hair raising experience the first few times... because some of them are quite curious and some are also attracted to emotions like fear, sex etc... I have personally enfolded these 'entities' and when projecting love to them they just seem to wonder off and leave you alone.
So the biggest problem you will encounter is fear itself... and unfortunately as mentioned before this comes from the many untrue stories we read about by writers who have no idea of reality, and no personal experience.

The second thing is that in the Emotional world we can think up some very scary stuff, and this can manifests as real as if it come out of a horror movie...Smile  but this is our own doing, and happens because of the fear factor. I know of many people who want to 'astral travel' for some reason but are just too frightened.

The old saying "There is nothing to fear but fear itself" is an esoteric absolute.

We are slowly being indoctrinated from birth with stories of doom by ignorant people who have one goal in their miserable life, and that is to keep others from reality.

Now lastly I need to just mention that in the lower Emotional ('astral') world there are humans who are discarnate and have a bad attitude, like many, right here in this world, and these Beings are often nasty to the point of being a nuisance... however you need to realise that lack of fear and standing up for your sovereignty is of prime importance in your life in the physical world as well as in the higher worlds... and it is NOT pie in the sky that we each have ONE 'guardian' known as an Augoeides who is 'assigned' personally to aid us through our millions of years in the human phase of our life...these light Beings do not bring us good luck, or gifts, or even advice when we need it, because they know that that would violate our right to self determination... but they do, and will help protect us from malicious intent by some very sad minded discarnate humans... who one day will see the light and the way to love and unity...as is our goal.
Take care...