'Destiny' and 'fate' are dangerous concepts for a psychic - especially for one who deals with precognition.
The difference between the two terms is that 'destiny' generally refers to a positive, divine event or state that should come to be (with a bit of human help), while 'fate' generally refers to a negative state or event that will come to be even if the person involved struggles against it.
Why are these concepts dangerous for a psychic?
Two reasons. The first reason is that the use of the terms 'destiny' and 'fate' presuppose a linear view of time - like a clock ticking away, always forward in one direction. The second reason is the illusion of imprisonment by time - a deterministic inevitability.
Basically, if the world is a machine (it is not), then there is no place for a psychic in it. A narrow, linear, deterministic view of time (and the dimension of life in general) closes up pathways in the mind of the psychic instead of opening them.
The psychic creates destiny and laughs at fate - this is the way to see past the illusionary prison of time.