In a way it really means dont give up. Like if you break up with someone and you are really hurt, "Get back out there" would mean work past the hurt and you will succeed and find happiness again because you have learned from this experience and the world doesnt stop because it happened. You have to continue trying

it means u need to go back as to where you went last..

get back out there mean go back to the place and do ur unfinish job and do it well kinda like that.

is not ka because ka means leave... or go away... and get back out there is not used with that meaning usually... 
"get back out there" is encouragement expression...

가~~~~~~in korean.