Humility

I actually think the song is about brexit but i prefer to think it being about someone getting over depression or a tragedy.

"Calling the world from isolation 'Cause right now, that's the ball where we be chained"

The singer (2-D or Albarn, although I really doubt that's the meaning he intended) is ready to leave his poor state of mind (the isolation) behind, since he's been chained to it so long, he's reaching out for help

"And if you're coming back to find me You'd better have good aim"

hoping they can help him (have good aim)

"Shoot it true I need you in the picture That's why I'm calling you"

He's found his will to move on (shoot it true) and repeats that he's calling out

"I'm the lonely twin, the left hand Reset myself and get back on track I don't want this isolation See the state I'm in now?"

the left hand is seen as dammed or impure in hinduism and christianism, he's saying that he feels insignificant or useless. But he wants to change his mindset (reset himself) and get back on track. Then illustrates how bad he's doing (his state)

"Callin' the hunter with a rifle 'Cause right now that's the ball where we be chained"

He calls out for a hunter with a rifle instead of an axe, as in red riding hood, so he's got good aim. He wants a hunter to save him and this dependance is the current ball

"If I pick it up when I know that it's broken Do I put it back? Or do I head out on to the lonesome track and let you go?"

He's pondering on what's it gonna be like if he's able to get better (pick himself up). Will it all be the same? Or will he never be able to get better? Forced to live like this or do something drastic.

The last part is a summary of his inner conflict

Get Better:

"I don't want this isolation" "See the state I'm in now?" "Do I put it back?"

Stay depressed or die

"I'm the lonely twin, the left hand" "If I pick it up when I know that it's broken" "Or do I head out on to the lonesome track and let you go?"