Want vs Need - ambiguity in small things to ultimate goals in life

Is there a real difference between what do we want and what do we need. Obviously we need air, water, food, shelter, sex to survive. But do we need all the generations of Iphone and Ipad or Mac air pro to survive. In fact do we actually know the difference between what we need and what we want.
What criteria do you think that will help us make a choice between what we want and need, if there is a fire at your apartment, what will you carry or choose to take with you. Will our ambiguity of want and need will interfere in our decision during a stressful or bad situations?
Do we go back to our instincts on making the choices in our life ? Because I could see this confusion of choice between want and need coupled with our inability to take a stand have made many of us to live without the well driven goal in our life. This is what makes us have unsuccessful attempts or lead a normal life. I am not much of exception... But we gotta learn to differentiate our life goals as well!! Let me know if these helps or any comments on this!!

Why do we pretend?

Why do we pretend and try to be someone else.?

I was watching SHERLOCK the BBC TV series and I was very excited and after an episode, I tried to be deductive to small details as does Sherlock, so I started to pretend like sherlock but didnt last very long after an hour or something I didn't pretend anymore, Then I watched another episode of Sherlock and started pretending again and lost interest in an hour.

I started analyzing Y.. why do we lose interest, This is very similar to the Gym workout, we start with high enthusiasm and then we just lose it and start finding excuses. This happens for many things in our life. Why cant we just keep doing it? is it cos of the hardship to do it? or simply we are quitters ? or our mind gets tired so easily over new things?

Now back to the question why do we pretend to be someone else? is it cos we are not happy with what we are? like Why only as a protagonist? Why Sherlock and not as John Watson? Watson has some special qualities... Will it be easy if we pretend as John Watson and we will stay in the character a lot longer than when trying to be Sherlock? How can we find ways to improve ourself ? How much or how long can a movie or a documentary or a book will leave an impact in our mind ? Is it possible to achieve it in normal advertising?

Mind Tricks the thirst for water control - A self experiment

I was just drinking some water from a Gatorade plastic bottle and got me wondering.... Why does Gatorade has a bigger opening than the soft drink bottles. So then I tried drinking water from a half liter Pepsi bottle and a half liter Gatorade bottle (when I was equally thirsty after an hour gap of time each time). I found that when I drank from Gatorade bottle I drank the water faster and I was even more thirsty after half liter of water than when I did the same from a Pepsi bottle (With a small opening).

Idea is Why not have bigger opening for the Pepsi bottles, that way will it sell more?? will people drink the Pepsi faster and will tend to buy another one to quench their thirst?? (Yes, water and Pepsi are different, I cant drink Pepsi at the rate at which I drink water because of the carbonated gas in the Pepsi)... Still I would love to see whether its the time consumed to drink half liter vs quenching of thirst... Wondering whether we just trick our mind that we are not thirsty anymore because we consumed the same amount of water for a longer time??

If this Idea is true, then where can we apply to create products and values to people.