I think one is always one self's worst enemy. Forget about negetive entities, just focus on your inner strengths and work on your weaknesses and mental blocks.
I've always had a problem believing in negative entities with an "independent power supply". Instead, i think of them more like something people create with their energy when they're scared, angry, etc. They may be perceived as being alive while they really just manifest as an image of one's fear or hatred or whatever.