"do one thing, and do it well"
That is my main motto for several years now.It keeps the clutter out of your head. Hope you will be able to achieve that!
Also do you know the MoSCoW-method? It is a way of prioritizing what you need to make
Perhaps it is also useful for you, read about it here: https://en.wikipedia.org/wiki/MoSCoW_method
I don't think I have heard it abbreviated as the MoSCoW method before, but I've seen the must/should/could/wont method before. Thanks for the link, it'll probably be a good thing to dig through and actually read the methodology behind it :)