One of the big reasons why you wont be able to go astral is when your body is damaged. If your physical body has any form of significant damage, the aura around the area will be missing or destroyed which will affect you on out of body experiences.
So lets say you had kidney stones and went to surgery but theres still permanent pain, you might forget that you will be ever coming out of your body until death.
irreversible aura damages consume way too much energy which wont let you burst out from it so easy. It causes a lot of stress and im pretty sure that you cant think right, let alone get good sleep with whatever surgery you might have if theres still pain afterwards.
shortly said: your body cant relax enough due to pain and internal stress on your organs and this will never let you out except if you manage it somehow to still relax. (And no, using pain killers or sleep pills will not help you repair the aura around it, yet you might try and it maybe works for you)
In the end its up to you if you try hard enough and use different methods until it works. Dont be discouraged, it doesnt mean that youll never be able to get an out of body experience because it takes a lot of effort despite damage.
A story of a body piling beaver
Time traps inside Dreams!
Are otherworldly contacts dangerous ? heres the answer