Dear John,
I hope this letter find you well, first I owe you a big sorry, that I break my promise and I couldn’t come to your place as I promised during my visit to your city Delhi.
Let me explain to you about my situation, as you already know I was working on a company project and due to that project, I came to Delhi to attend a company meeting. However, I was about to come to your house after the meeting but suddenly I got a call from my boss and he asked me to come back as soon as possible after the meeting. Actually, the problem was my boss wants to see my project presentation papers before the company annual project meeting, but that paper was in my desk shelf locker and by mistake, I carried the shelf locker key with me. So, at that point, I had to go back and couldn’t come to you. I hope you will understand and forgive me. One more good news, in our company annual meeting everybody like my presentation and I am been promoted as a project leader now.
As compensation for my mistake, I want to invite you and your family for Christmas eve. I know you also have off during Christmas and it is being a long time since we meet each other. Do you remember Peter? our old college friend he just recently come back from the USA. I also invite him to a party. It is going to be our get to gather with our old friends.
I hope you will accept my invitation and come with your family this December.
Yours faithfully,
Sammy. 
Dear John,
I hope this letter find you well,  
first
 I owe you a  
big
 sorry, that I break my promise and I couldn’t  
come
 to your place as I promised during my visit to your city Delhi. 
Let
 me  
explain
 to you about my situation, as you already know I was working on a  
company
  project
 and due to that  
project
, I came to Delhi to attend a  
company
  meeting
.  
However
, I was about to  
come
 to your  
house
 after the  
meeting
  but
  suddenly
 I  
got
 a call from my boss and he asked me to  
come
 back as  
soon
 as possible after the  
meeting
. Actually, the problem was my boss wants to  
see
 my  
project
 presentation papers  
before
 the  
company
 annual  
project
  meeting
,  
but
 that paper was in my desk shelf locker and by mistake, I carried the shelf locker key with me.  
So
, at that point, I had to go back and couldn’t  
come
 to you. I hope you will understand and forgive me. One more  
good
 news, in our  
company
 annual  
meeting
 everybody like my presentation and I  
am been
 promoted as a  
project
 leader  
now
.
As compensation for my mistake, I want to invite you and your family for Christmas eve. I know you  
also
 have off during Christmas and it is being a long time since we  
meet
 each other. Do you remember Peter? our  
old
 college friend he  
just
 recently  
come
 back from the USA. I  
also
 invite him to a party. It is going to be our  
get
 to gather with our  
old
 friends.
I hope you will accept my invitation and  
come
 with your family this December.
Yours  
faithfully
,
Sammy.