I used something similar: 750words.com for a year
within few months the streak turned to torture.
There was no noticeable improvement in my adult writing skills yet I felt obliged to keep the chain going.
The happiest day of that year was when I mixed up time zones and missed one day.
Have not written anything seriously since.
It sounds like a full time job.
The problem stemmed from dearth of possible topics.
Thus my writing degenerated into some sort of free association chains reminiscent of most blogs.
Get those 750 words done and you can get on with your day!
Maybe an Edgar Wallace inspired topic generator would have been handy.
It seems like some people do get into dark places when they break their chains. I've considered several times having a limit that would prevent you from writing 30 days in a row or something.