I stay on the 15th floor and quite often climb up the stairs, after my morning workout. 

And I love playing tricks with my mind. 

Usually I climb up while looking down, thinking about something, not consciously counting the floors. 

And then one time, I did notice the floor.
It was Floor 5. 
And my mind instantly went, “damn – all the hard work done until now, has to be repeated 2 more times”. 

And then one time, I did notice the floor.
It was floor 8. 
And my mind instantly went, “ok – just repeat what you have done until now and you will reach”. 

And then one time, I did notice the floor.
It was floor 10.
And my mind instantly went, “just half of what you have done until now!”

And then one time, I did notice the floor.
It was floor 15. 
And my mind instantly went, “wow! Its done?”

And then one time, I did notice the floor.
It was floor 16. 
And my mind instantly went, “holy shit. I didnt even realize it!”

There are so many ways we can trick our minds. And all of them begin with not tracking what milestone we have hit so far. Instead focusing on the climb. 
And keep climbing!