Every time something comes to an end, something else begins. So is it the end of a beginning or the beginning of an end?
Well, they are simultaneous events, in any story. Hence, the end of a beginning is the beginning of another end. Therefore, the first sentence cannot be written until the final sentence is written.
Every action has a consequence. That pretty much sums up everything. Any action you take has a start and end; that start could be the ending of the previous action, and the end could be the beginning of the consequence. Thus, every beginning is an end, and every end is a start.
Going-Back-to-the Beginning-
Because we are anxious and insecure, we tell ourselves that a better beginning will give us the momentum we need to reach the end. But it won’t. It doesn’t. There are four challenges writers face when they sit down to write. 
The first one is procrastination. The fourth is – The Going-Back-to-the-Beginning.
There are various reasons that writers use for going back to the beginning instead of proceeding into the messy middle or sneaking up on the end. It’s comforting to return to the beginning, the status quo when things weren’t falling apart.

• Fight or Flee

Every time your characters get into an argument, one of them leaves the room. Leaving is the first impulse in – a situation that might be uncomfortable.
You probably recognize the term “fight or flee.” It refers to the physiological response we humans have to perceived threats, whether those be mastodons, marital muddles, or the messy middle of a manuscript. Regardless of the risk, some of us are more apt to fight than flee. Fleeing doesn’t solve anything. Don’t go back to the comfort of the beginning; stay in the messy middle and fight.

• Taking a good trip

So, why doesn’t a better beginning give you the momentum you need to sprint to the finish line? The answer is simply that the beginning is speculative. It’s a guess. Writing a book- length fiction is a long journey into the unknown and even if you do all sorts of advance planning, you cannot foresee all the adventures you have ahead of you. If you could, taking the trip would not be all that much fun, now would it?
Writing the beginning of your novel is akin to packing your suitcase for an expensive and lengthy trip to a far-away place. You haven’t been there yet, so you don’t know for sure what you’ll need. When you get back, when you unpack, you will know, for instance, that the hiking boots or the high heels were just extra weight. You never got a chance to hike. The umbrella did come in handy and so did the granola bars, though you ate those in your hotel bed and not on a path. Chant — the best-laid plans — to yourself, whenever you imagine that repacking your suitcase is somehow going to make a difference in a trip you haven’t yet taken.

• The Hindsight

If you could retrieve the many hours you have spent rewriting the first chapter of your first novel, days, weeks, even months would be yours again. At this point, you could and would use the time more profitably. Favouring editing proofreading is correct but the occasion for revising the first chapter is after you have written the last one.
Conclusion
Little actions have consequences, too; what you must take away is that everything you start comes to an end, and endings lead to new beginnings, so make sure you start things that have happy endings and fruitful new beginnings.