Pareto's principal is that 80 percent of the result is due to 20 percent of the work. Obviously every situation is different. The point is some activities are more productive than others, much more productive. The reverse of this is the problem. The more results you want the exponentially higher effort it will require. Running under 17 in the 5k took me about five years of serious running. Doing that eight and a half times in a row still has not happened after another seven years.
The moral of the story is if you have high hopes for something you better get started right away because it is most difficult near the end.