Actually, fear of success is a very real situation - but it is VERY closely related to the fear of failure.

For many people, success means pressure - if they do well or win at poker or get a great job, then immediately, it can create anxiety - what if I lose this job? What if I lose all my winnings? etc.

So what these people will do is they will protect themselves from those potential failures by sabotaging their chances to be successful. That way, they can stay in the same situation they are in - one that is likely very comfortable for them, even if they are miserable - because at least this is misery that they understand and know they can deal with.

Thus, fear of success is closely linked to fear of failure.