Is there a single word to qualify/describe someone that causes his own misfortune, or even a single noun that refers to such a person?
causing the same problems that you were intending to solve
I suggest hapless (from Merriam-Webster):
: having no luck : unfortunate
listed synonyms: unlucky, hard-luck, ill-fated, ill-starred, jinxed, luckless, snakebit (or snakebitten), star-crossed, unfortunate, unhappy
In addition to hapless, as suggested by Cornbread Ninja, I'd also suggest inept carries similar connotations (from the Random House Dictionary, via Dictionary.com):-
- without skill or aptitude for a particular task or assignment; maladroit: He is inept at mechanical tasks. She is inept at dealing with people.
- generally awkward or clumsy; haplessly incompetent.
- inappropriate; unsuitable; out of place.
- absurd or foolish: an inept remark.
Inept carries with it the idea that one has voluntarily exposed oneself to the sort of situation where these things apply.
Someone who subconsciously undermines his own success is inflicting self-sabotage. Someone who sabotages is a sabotager or saboteur, and we can combine "self" into a word by replacing it with the "auto-" prefix, hence: autosabotager, or autosaboteur.
Of course, this is a rather narrow nuance. This question seems to have a broader interpretation.
For instance, someone who suffers setbacks due to making foolish mistakes isn't inflicting sabotage; that psychological element is lacking.
Words used for someone who brings avoidable calamity on himself by his own foolishness, and not through any bad luck, are simply general words that denote any sort of fool: buffoon, incompetent, imbecile, and so on. In all the myriad words that describe a fool, there is an understood element, almost by definition, that this is a person who causes bad things to happen to him or herself and others due to poor planning and reasoning.
What about someone who doesn't lack intelligence, but suffers setbacks due to exercising poor risk management? When a calamity occurs due to bad luck, luck cannot always be blamed; sometimes bad luck calamities could clearly be avoided by reasonable steps to manage risk. People usually do not intend for traffic accidents to occur, yet these are caused by mistakes and unnecessary risk taking, and blame is assigned accordingly, not simply on bad luck. Those who take unnecessary risks can be described with adjectives such as careless, irresponsible, nonchalant or blasé (with regard to risk). "His nonchalant attitude always lands him in a bind."
King Midas might be appropriate.
There's also the "Midas touch" which is generally considered a good thing (everything you touch turns to gold) but the original story is a tragedy (he turns his daughters to gold) which he brings upon himself via greed.
Or if he just trashes everything, there's King Midas in reverse.
In The Netherlands there is a writer, poet and performer known as Johnny the Selfkicker. Paraphrasing Wikipedia, the Selfkicker "has proven to be worthy of his name because of wild, often haphazard performances, during which he never fails to work himself into a frenzy, which often results in him collapsing right in front of an astonished audience." Download a picture of the Selfkicker at http://sdrv.ms/18EwcKs . Johnny even looks the part of the selfdestructor. I'm sure the Selfkicker would love to have his name officially adopted by the English language.
PS When and how does a new member acquire the right and ability to attach a picture?
Depending on the severity/seriousness of the outcome I guess you could also use the following terms:
a monstrous creation; especially : a work or agency that ruins its originator.
a thing that becomes terrifying or destructive to its maker.
a person who creates something that brings about his ruin
The corresponding idiom is Frankenstein's monster
Giving extra powers to the army turned it into a Frankenstein's monster that is now threatening to overthrow the ruling party.