Oh I’m definitely in the non-legit camp! I don’t have quite the situation of @marcmarti. Actually, I don’t have that situation at all. Except from the fact that I, too, paid about $400, a bit more than that, in derails over a similar period of time. And I, too, have written about it. Somewhere… where is it… here:
@zedmango re: slippery slope: Yeah. I feel you.
Including this bit 
What I do is: I tend to have a fairly solid understanding of why I need and made a goal in the first place. Commonly this is because time just pours away when I watch video or surf the web. If Beeminder makes me not do that then I consider it a success.
That is for indoor goals.
I got one mainly outside goal and the reason I have it is because I would otherwise lazy potato and stay inside when it’s perfectly good weather to do something outside.
So consequently, if I can’t meet my goals because I got a strong headache that lasts multiple days usually, I call non legit. Or when some social event comes up. Because that’s not the problem why I joined Beeminder. It’s not why I made these goals.
When it’s raining cats and dogs outside, I call non legit on my outside activity goal. Because, again, I made the goal so I wouldn’t potato when it’s perfect bike weather. Not to drench myself and risk a cold.
I can already see @dreev getting the pitchfork ready I suppose it’s a different philosophy and I have to say that when I was new to Beeminder I was more strict with this. Which was both good and bad. It created stress (positive stress) and ultimately I got things done a day earlier than I would have otherwise.
But this one day of progress did not matter because it’s all about steady progress, not what you do in one single day.
On the other side I got into silly arguments with friends to whom I had to say no because I didn’t have time. Because some random website wanted to make me do something, completely oblivious that the outside variables changed. I would have never beforehand said “Yeah let’s work so much this day so I can’t attend my friend’s invitation”.
I have previously mentioned that the 7 days akrasia horizon does not work for me:
Hope this helps looking at it from a related perspective 