This is actualla a very important topic that you posted here Kiya..
Why??
For me the frase "Get a Life" is as you said it almost every time meant in a Negative way.. The reason is that the people who says it dont have the life they wants,or dreams off..
In Norway we have this new thing, SMS programs at night on the tube.. There people is sending in SMS to be read on the screen,they chat about nothing and everything.. What I have noticed there is that there is always someone that sais "What do you people do this for? using money to chat at TV, get a life"
There is the frase used again.. "GEt a life" Then I tend to wonder.. Why in the heavens name do they complain about people chatting there?? When they obvissly are doing it themselves?? It is not that they are looking down on the people that is doing it, they dont like themselves.. They have a poor selfimage and to compansate for that they talk negative about others.. Too feel good about themselves.. So my point is: If you just accept who you are and what you are doing, this problem wouldnt be an issue..
I know that this never is happening, the human mind is to complex.. But if we are doing it and always are positive, we can influence other "negative" people too get more positive attitude.. Becouse who doesnt want to have a good life..
Ftr: My answer to your 4. question is: A life to get is a life were you are happy with yoursel and your enviroment.. That you like yourself..