There are two common ways this habit increases people’s difficulties.
First, they assume that they know what is going to happen, so they stop paying attention and act on their assumption instead. Most of what they assume is wrong.
The second aspect of this habit is playing the mind-reader and assuming you know why people do what they do or what they’re thinking.
Wrong again, big time. More relationships are destroyed by this particular kind of stupidity than by any other. Adrian Savage