Change Topics to Light Ones

If a topic is becoming depressing, change it up and make it lighter! Sometimes a small amount of positive energy is all that is required to move a conversation in the correct direction.

Try these tips following:

• Using tone and body language to make the situation humorous.
• Bringing up the positive sides of the issue at hand.
  
• Making nice jokes with the person (works best if you know them well!).
• ...

Of course, not everyone who is negative will well respond to these. However, some people will return to "normalcy" as soon as you change the topic, while some people could be distracted by your lively and happy energy.