As a weekend project, seems like you're off to a good start here. The UI is nice, as I happen to like simple, clean, minimal interfaces. (This is bootstrap, I assume.)
I'm not keen on the flow of creating & editing questionnaires, though; would prefer having the whole process be done within the same screen instead of jumping to a new page. This is especially the case when mobile.
It's unclear if not being able to have multiple questionnaires active simultaneously is by design or a bug, but in my mind it's essential. There are a few things I could stand to be reminded of needing to do routinely during the day (i.e. take a 5-minute stretch break from coding every hour), some other tasks where I'd like to track how long I'm doing them over time (how much sleep, how long the workout was, etc.) plus a ton of possibilities I'm not even thinking of but would likely find really useful.
You might want to consider adding some scoring, rewards and achievements to the mix as well; it might make the journey of reaching your goals a little more fun.
I'd like a checkbox-based multiple choice questionnaire in addition to the radio button-based one you currently have. You'd have to complete all of the tasks for the questionnaire to be considered complete. Partially completed questionnaires provide lower scores than fully completed ones.
Also, the ability to add this as a channel to if-this-then-that (http://http://ifttt.com/) could turn out to be really powerful. Since this is yet another calendar in my life I would like to find a way to fit it into the one that rules them all. Not sure what that means, really, other than I have multiple calendars that I've taken the time to sync together, so this should as well, somehow. ;) Perhaps there's a way to take a recurring event that I've created on my calendar that Routinetap could trap and automatically turn into a questionnaire.
Lastly, Maybe I want to tell my social circle that I've reached some milestone or completed a goal; ifttt could provide that without you having to do much work at all (i.e. send an SMS or email to me when the milestone or goal is reached; on ifttt I could set up a trigger that blasts my achievement to my social networks, or something else entirely). If you're not familiar with ifttt, you should check it out. It's awesome.
Again, a very nice start. I think you're wise to get this out there as a MVP; I can envision this turning into a very useful product/service.
Feel free to ping me here on HN for more discussion. ♒ Cheers.