the leeches will constantly convince you that you owe them something, and so although you may not even like them, and may wish for nothing more than for them to fuck off and die, they nonetheless will coerce you to devote every bit of your life to them.
they make it very difficult to register a sensation or think a thought when you are around them. and when you do think a thought, to them this is the equivalent of expressing this thought as being your opinion, and so you can only think thoughts that you would be ready to express as your opinion when you're around them. this is a little more than damaging of one's ability to think, and if this then forces you to be more talkative, they will not be very sympathetic towards that either.
if there is something that can be criticized about the thought you are thinking they are made to bark at you then as well. these will often be good criticisms that you yourself will make regarding your own thoughts if given a chance to. but when they get to it first, it doesn't fill you with desire to then make these criticisms, and so they are not exactly helpful, more damaging than just useless, and there is really nothing much better that they can do than go away.