Of course you cant be picky, beggars shouldn't be choosers, or something like that - but most serious, rewarding positions with established companies that have healthy work-cultures and reasonable bosses don't interview based on questionnaire checklists made by third-parties that have questions like "what is your biggest weakness".

So you don't really have to worry about this sort of question once you get yourself established or go after the right opportunities. If you do get asked it in one of these diamond-in-the-rough companies, its generally a sign that the hiring manager doesn't understand the requirements for the position and is relying on generic questions. You can use this to your advantage by stating some sort of reverse compliment like "I tend to focus on my work until things are complete and don't take enough personal breaks. I have been utilizing a personal calendar at work to ensure there's enough balance between everything and I have seen a lot of success because of it." Then perhaps make a direct reference to a previous incident/something on your resume.

But seriously, don' fret over this question too much. With a little luck and some hard work you won't even be exposed to these types of interviews. But again, beggars cant be choosers so I completely understand if some people are obliged to apply for these types of positions.