Get a life! – Займись чем-нибудь интересным!/Не переживай из-за ерунды!/живи полноценной жизнью!

You spend ten hours a day playing computer games? Get a life!

 

For the life of me – никак, ни за что

Why, I can’t  do it for the life of me!

 

Not on your life – ни за что на свете

Choose something right now?! – Not on your life!

 

He’s the life and soul of the party. – Он душа общества.

 

It has a life of its own. – Живет своей собственной жизнью. (про неодушевленный объект)

The painting seems to have a life of its own.

 

This is the life! – Красота!

(something that you say when you are relaxing and very much enjoying the fact that you are not at work)

 

That’s life! – Такова жизнь! Ничего не поделаешь!

I’m disappointed with my results, but that’s life.