Life is a set of limited number of days blessed upon us by God without mentioning the upper limit. What we do out of this is completely left to us. As days pass on many of us look back at our past, some with grief, some with regret while a few with satisfaction. Some with grief because they couldn't do all that they wanted to, some with regret because they didn't do all that they wanted to and some with satisfaction because they could a bit of all that they decided to. All that you must do shall form the cardinal rules of life.
Time just escapes at its own pace and doesn't wait for us to take any action. It's left upon us to run along with it to make things fructify. The reason that many don't achieve all that they want is not that they didn't want to. Simple and the silliest reason is that people tend to forget what they wanted to do. People remember those work that is enforced by others and constantly reminded of or those work which can satisfy their immediate necessities. After about one or two decades they end up just regretting for having lost all the time to make any difference at all. So it's very important for us to divide the work towards our goals and dreams into daily activities. All such daily activities that shall take you towards what you want out of life shall be entitled with certain must-to-do rules and they shall be called as cardinal rules of life. "I must workout in the gym everyday for 90 minutes to have a healthy and fit body", "I must write a blog everyday to develop myself into an author". These are examples of some simple cardinal rules that I make for myself.
Make sure that your cardinal rules are a combination of both your work and target. The moment you read your cardinal rule, it must remind you about your goal as well as the work that you must do to attain the same. This is one of the practical ideas that I designed for myself for a better productive time usage. Do let me know if it helps you as well on firstname.lastname@example.org