You probably meant what hinders you from astral travel when the energy level in your astral body is low.
If you read our book:
than you would know but lets make it clear.
Our astral body itself doesnt need energy to do anything besides ourselves, the soul (which has unlimited energy). But our physical body of flesh needs energy! And with energy i mean the cosmic or planetary energy which can be loaded while meditating and relaxing/sleep (in meditation way more!).
This energy form is like a booster to the switching point when the body’s are changed in the night and for the physical body to have energy for the coming day. So to answer the question, the more you use your physical energy up – the more problems you will have to get out because you will not have any energy to spare. It is comparable with the start of an engine while the battery is running really low. And do not mistake food as an cosmic energy source for your physical body, it is not!