Slow and steady progress

You take another deep breath before heading up to the fourth floor. You count the steps as you ascend. Ten steps. Turn around. Ten more. Fourth floor. You lean on the handrail to catch your breath, making sure to not rush. You're not winded yet but you're sure you will be very quickly if you don't pace yourself.

You focus on just one step at a time, one floor at a time. Not thinking about how many stairs you have left total helps you just get to the next floor each time. Slowly you ascend higher and higher. Fifth floor. Sixth floor. Eighth floor. Twelfth floor. Stopping at each floor is definitely helping you make steady progress. You're already over halfway there and you aren't winded at all!

As you pause on the 13th floor, you hear the distinct sound of a door swinging open and latching back shut far below you. Whoever just entered the stairwell makes slow steps up or down the stairs, to the next floor. You then hear another door open and shut, and the stairwell is silent once again. It's only now that you realize how quiet this stairwell has been this whole time. Your curiosity gets the better of you and you peek out the door to the 13th floor. When your head pokes into the hall, your eyes go wide by the familiar bustle as far down as you can see. You pull back into the stairwell and let the door closed as quietly as possible.

With another deep breath, you begin slowly ascending to the 14th floor. You hear not a single sound except for the light patter of your footsteps as you methodically cover the second half of your journey. 18th floor. 19th floor. 20th floor. Your goal is almost in sight!

You climb the last 20 steps faster than any other flight you've covered so far. Your last few triumphant steps are spent staring at the plaque next to the door and the text embossed into it. "21". You've made it. Though you still aren't exactly sure where you've made it to. The receptionist said you'd know where to go from here, but you still have no idea what is on the other side of this door.

There's only one way to find out, you suppose.