The Legend of Zelda: Majora's Mask 3D

So, is it really easy to mess up and go over the time limit thingy or would you need to purposely delay everything as long as possible to, what i assume, game over with it?

It's literally impossible to beat the game in the first 3 days, there's a mechanic given to you via an item to go back to the start of the 3 days. with only certain items you've obtained being retained, and you also get methods to slow or even speed up the flow of time. You do have to manage your time, but at the same time it is still rather forgiving. The worst that can really happen is you lose some progress on a side quest and have to start it over if you don't do it quickly enough.