Learn English – Get a life | You have no life

The phrase is usually "get a life" rather than "get some life." The person who says this feels the person to whom it is said is wasting his or her time on something. Wikipedia has good examples:

http://en.wikipedia.org/wiki/Get_a_life_(idiom)

Implied in the taunt is to act normal (whatever that is!) or mainstream.

The meaning may depend on whether the person hearing it speaks British or American English. Being British I thought the third use of 'can' referred back to the second, but switching from verb to noun, giving the meaning:

1) Get everything you are able to get

2) 'Can' your gains (keep/preserve them, put them away)

3) Sit on that can (that is, guard your gains so no-one else shares them).

I didn't immediately understand 'can' as 'toilet' as the use is rare in Britain.

There is a page though from a blog by an (American?) HR consultant dated December 2011 and headed 'Get all you can. Can all you get. Sit on the lid.' which suggests it may also have had the same meaning to Americans once. http://www.thebuzzonhr.com/2011/12/21/howto_setprioritiesanddelegate/