Theory:

     Of all the things I am not very good at, living in the real world is perhaps the most outstanding. I am constantly filled with wonder at the number of things that other people do without any evident difficulty that are pretty much beyond me. I cannot tell you the number of times that I have gone looking for the lavatory in a cinema, for instance, and ended up standing in an alley on the wrong side of a selflocking door. My particular specialty now is returning to hotel desks two or three times a day and asking what my room number is. I am, in short, easily confused.
Explanation:
 
The introductory paragraph of the lesson is important because it sets the tone for the entire lesson. The narrator begins his narrative by declaring that he is poor at almost everything in the world. He says, "living in the real world" is something the narrator cannot do. Moreover, the line "of all the things I am not very good at" suggests that the narrator is not good at so many things. The line also indicates that he is quite critical about himself.

The line "of all the things I am not very good at, living in the real world is perhaps the most outstanding" also describes the kind of humour that the writer has used in the lesson. The humour is worked on the ignorance or the stupidity of the narrator rather than on somebody else. Hence, it is self-deprecating.

The narrator, as declared before, is quite inept in doing a lot of simple things. He says that he has found himself in several 'hard' situations that people generally consider normal.

He recounts a couple of such recurring situations. For instance, when he looks for a lavatory in a film theatre, he kind of gets lost or ends up locked in a room or alley with self-locking door. Unfortunately, he would either have to take a detour to reach his destination or might get stuck inside until he attracts help from the other side of the door.
 
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The narrator ends up standing in an alley

The narrator is also forgetful in nature, and he often forgets his room number whenever he is staying at a hotel. As a result, he had to pay frequent visits (two or three times in a day) to the hotel desk to find his room.

Hence, it is evident that the narrator is forgetful, clumsy, and is "easily confused".
 
Meanings of difficult words from the paragraph:
 
S.No
Words
Meanings
1
OutstandingThat which is clearly noticeable
2
LavatoryA toilet
3
AlleyA narrow passageway
4
Self-locking
That which locks automatically
Reference:
National Council of Educational Research and Training (2006). Moments. Accidental Tourist- Bill Bryson (pp. 56-60). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.