If you want to mediate successfully then:
a) ask for the protection of the supreme being at the very outset - make it the first thing you do;
b) ask that those influences which will assist your journey make themselves known to you.
Entities within the astral are not always what they appear to be. Question everything you are told. Trust nothing. You're on your own.
Sometimes you need to experience dark shit to move forward. Other times you need the light. This is why you always invoke the protection of god first. This way if you encounter something horrible which is necessary for your growth, it cannot harm you.
Alt you can just relax and chill. Just do a) first.