The game development might be slowed down due to minor things

I have just discovered for myself that game development implies many routine tasks. 

Here works the Pareto principle. According to the Pareto principle (aka 80-20 rule) you will spend about 80% of development time developing functionality which is going to be used only in 20% of game time.

The implementation of all these menus, settings, score systems and etc ... all it takes a lot of time! I've implemented a game within a week! But as for this "wrapper" for the game, I have already spent three weeks and still have not finished.

Here raised a reasonable question - why does it take so long? I encountered two major problems which I want to describe further.

1. A lack of information

Actually the problem is that there are a lot of studying resources which are all about "how to create a game" but there is only a bit information about creating the main menu, the menu with the settings, a pause menu, score counting systems and etc in them... It really takes hours to experiment with different stuff to get something that really appropriate for the game and something that works as you wish. In fact, it is the place where another problem comes from.

2. It is difficult to refuse already implemented ideas

I have noticed an interesting fact. It is possible to spend a lot of time implementing some cool effect or feature and suddenly realize that it is absolutely not appropriate for the game or it steals the show. Once you have realized it, it is very difficult decision to throw this feature away either because it's cool or it took a lot of time to implement.

How not to slow down the development speed? The interesting thing is that there is no right solution, rule or an algorithm to avoid this. The only thing you can do about this is to practice more and find something appropriate for you. Find out your own best practices.

I want to share my own best practice which I use while implementing minor features that were not initially paid enough attention.

Firstly, set a clear goal. Statement of the goal should contain a clear criteria of achievment.Secondly, set a timer which reminds me every N minutes to look at the goal one more time. It is a good moment to check if you still go towards your goal or have already lost the way. 

In other words, this practice is similar to hiking with a map. You have a destination point and every N meters/miles/hours you check if you are moving in a right direction.

Have you ever had the same or similar problems? Could you please, share your experience?