What do you call a person who prevents his/her own progress?
Solution 1:
Consider Jonah complex:
The Jonah complex is the fear of success which prevents self-actualization, or the realization of one's potential. It is the fear of one's own greatness, the evasion of one's destiny, or the avoidance of exercising one's talents.
(Wikipedia)
Solution 2:
The behaviour is called self-sabotage (a Google search shows many articles about it).
But I don't know a word for a person who self sabotages. Self-saboteur is used but sounds artificial to me.