If I can chime in here, I'd like to just offer some general life advice that should apply here. Whenever you set out to do something (just starting), you are almost never ready/prepared for it. You can come up with all sorts of reasons why something might not work, and some of those things might be good reasons, but you just have to say "eff it" and start. You'll come across obstacles and you will overcome them and move on.

In the case of astral projecting, I can tell you right now that the food you eat isn't going to be what holds you back. Fear will most likely be your main obstacle throughout your "journey". But whenever you have concerns, just remember that you will get past them and that you will move on, just like everything else in your life.