Why Men and Women do not know how to appreciate Happy Endings instead get Sour Beginnings ?

Right so I am not talking about "Happy Endings! " like -  When a masseuse feels inclined to finish your session w/ oral sex or manual release (usually for an extra twenty dollars)

I mean " Happy Ending" which every Men and Women wants - one like Movies.
They finally walk towards sunset or get married.

The problem is they are great stories falling in love despite differences, odds, the chase, the problems and finally conquering them and Finding the " one". It is a great fantasy !!!

Like Movie " Yeh Jawani Hai Deewani "

https://en.wikipedia.org/wiki/Yeh_Jawaani_Hai_Deewani

If you watch carefully there are 2 love stories 

1. Naina and Bunny

2. Aditi and  Avi

Even though whilst Naina and Bunny seem to be protagonist and overwhelm in movie. There was also a Love Story which has a different ending between Aditi and Avi. 

Or 
Movie like Kabhi Alvida Na Kehna. 
https://en.wikipedia.org/wiki/Kabhi_Alvida_Naa_Kehna

It is interesting story of 2 couples who are really unhappy with their marriage. Really unhappy and they know it. Things they say to each other is nasty. Dev and Maya fall in love and afterwards have an affair. However despite their heart aching for each other. After 3 long hours of movie there is no way that Dev and Maya would know whether they are even compatible or how it is to live with each other on daily basis. More on marriage here Marriage Material 

Because Marriage as an institution despite seems very simple is complicated. Relationships formed are complicated and very few people know how to spend rest of their life with someone. Maybe that is why Marriage Anniversaries become more important. However ofcourse whether Anniversaries are great way to quantify quality of relationship of husband and wife is debatable.  I am still exploring and my ideas of marriage and it has always made me curious " Why marriages end up in Divorces? "

The following video would make think more on Marriage and person you ultimately marry.
Traditional Marriage v/s  Romantic or Love Marriages. People thought Love Marriage was an answer and we are still left with some of the bigger questions which are asked by this video. 

Sometimes Love Stories are Tragic like Romeo/ Juliet, Titanic Rose and Jack etc and thus Memorable. Hollywood/ Bollywood, Novels, TV give us plenty of love stories but clearly no guidance on what to do when we have got the one. Because when have got the one 

We soon realize is that it ? Does life has only this to offer me ?

Like things in life - We born, we  go to school, then university , get a job, find somebody to love, have few children.
Question always remains is that it ? Does life has anything more to offer?

I never understood why Film Notebook was so popular ( I kept on thinking notebook computer...lol... )
https://en.wikipedia.org/wiki/The_Notebook_(2004_film)
until very recently when I saw what happens to Allison. She transformed in the company of Noah to be carefree woman she always was.  I feel that every person who marries and decides to live with someone goes through major transformation. Perhaps somewhere we need to hold on to being who we truly are whilst this major transformation and responsibility thing happens. 

Unless one has

1) Real purpose in their life and bring best not only in themselves but in their partner too

2) Ability to everyday make best of it and not take partner for granted is hard work for both Men and Women. 

However question is always that whether ONE person can be whole world ? Is it even fair to expect one person to become their whole world and expect one person to fulfill all their needs? Would it be right to be so possessive or to expect so much ?

Thus I feel sometimes Happy Endings can become Sour Beginnings ! if you or your partner is not appreciated. Thus Happy Loving !

I am Loving it ! - Hope not as Mac Donalds Fast Food but hope we can enjoy marriage as much as our Favorite Fast Food. 
Hope your The End is a new beginning of long slow journey ahead.