If you want to get things done in a sustainable fashion, here are 3 essential laws for productivity. 

1. Parkinson's Law

It states the work expands to fill the time that we allocate to it. So, if you want to get something done, try giving yourself less time and see what happens. 

2. Pareto Principle

It states that 80% of the results often comes from 20% of the inputs. So, what you want to do is figure out what is that 20% thats driving 80% of your output and then you can kind of ignore the rest, if possible. 

3. Newton's First Law of Motion 

It states that an object at rest continues to stay at rest but an object in motion continues to be in motion. So whenever you're struggling with procrastination, you should remind yourself this law. You can remind yourself that if you can just get started, it'll be way easier to keep going.