I haven't had much astral projections in the last year or two because I haven't personally been trying to project.
I've never really tried to protect myself before I project and I just simply go ahead with it. I just personally believe within myself that nothing can harm me and that I have total control of myself and would never let any other entity to take control because I don't belong to them and that they don't own me, mind you their presence can be very intimidating at times.
I have had my encounters with a few negative forces. I just simply yell at them and tell them to go away and that I don't like their presence. You have to yell with conviction and with a high sense of authority. If you ever tried to intimidate someone and you succeeded, that form of energy is the type of energy you have to project when you do meet some entities that makes you feel uncomfortable.