The best piece of advice I have ever received as far as productivity was B.I.C.
Put your Butt In the Chair and write. This is harder than it sounds. Even for someone who loves to write there are going to be those days where the prose comes slow and it feels more like work than fun. You will think of all of the other things you could be doing instead. Maybe some of those things even need to be done, just not right now. Now it is time to write. Now it is time to sit in that chair and put words on paper. (Or on the screen depending on your preference.)
It takes discipline and stubbornness to write. Don’t let a difficult paragraph or chapter over come you. Don’t fall prey to the siren call of dirty dishes or laundry. Write. Write Now. Practice the rule of BIC. (Then give yourself permission for a cup of tea.)