Is there a word that describes someone who continually tries something but always fails? This isn't describing in the positive sense - as in someone who never gives up - but more about the negative side of always failing.
Examples would be someone who creates many failing businesses, someone who can never stick to a diet or someone who cannot remain faithful to their partner.
More context would help narrow down the possible words that might fit for this person. Why do they fail? Are they aiming too high and can't attain the skillset needed to achieve success? Are they lazy? Do they lack the intestinal fortitude to follow through on a goal? All of these scenarios conjure different words to describe such a failure. – Kristina Lopez
I'll give you an exact example to narrow it down more: A person who tries to diet and exercise but they always cave in and eat unhealthy stuff and/or skip exercise, despite knowing it'll be bad for them. Someone who's perfectly capable of doing it, has a sound mind and knowledge of why and how they should do it, but regardless, still fail each time they start doing it after a short while. I'm not talking about an unlucky person or a person who's too stupid or naive to achieve it.
However, I don't want the word to be specific to dieting (like "fatty" :P) but a word that could be used in other (albeit similar) contexts too. Hope that clears it up.