This is saying that you can have and do anything you wish in your total existence but unless there is balance you will not be happy and in harmony with your self. 

Any extreme whatsoever will cause problems of one sort or another - and these problems will - without doubt, bring unhappiness. 

Picture for yourself a pair of scales and imagine just how difficult it is to achieve perfect balance upon them. It is the same in life. 

You want what you want in great measure and it is not until you are able to realise that too much of any one thing cannot bring you happiness and contentment, that you will be able to consider yourself wise.

So look upon Karma as your friend in your life. See in your mind those scales out of balance and realise that, with patience you will  be able to set the balance right.

A Hint..........If you try to treat each person and each situation in the best way you can, your scales will be very close to balancing.   

When you are not happy with what you have created in your life, look within for the answer - not without. 
Remove that which is causing imbalance before Karma does it for you - it will be less painful