It's like a loud voice in your head drowning out any other.
It's the voice in your head twisting a reasonable course of action into one that seems unreasonable and unthinkable, while it makes you take an unreasonable course of action, because it's telling you that if you take the reasonable course of action, the worst possible scenario will happen.
It's the voice in your head telling you to pity yourself, that you should be sorry for simply existing.
It's the voice in your head telling you to isolate yourself, because if you don't others will judge you and hate you because it's telling you you're a terrible person who's wasting their time.
It's the voice in your head telling that it's the only thing keeping you from being a worse person, that it's the only thing keeping you in check.
It's the voice that demands you do what it wants loudly.
I have found that even though it drowns out other voices... there are some it cannot drown out, once you listen to them. Another, more confident voice, strengthened by the support of friends; emboldened by the knowledge of what one is capable of; and actualised by the desire to finally get rid of it.
No more listening to that voice, which has interfered with so much, and helped never.