How can I stop my Facebook Status being shared beyond my named friends?

http://ift.tt/S82hJS

Twice in the last week friends have shared my personal status with their own friends (no idea why! I’m not that interesting) but the point is that I shared the status with my friends and did not appreciate them be shared with other’s friends.

I’m happy to have any links, pictures etc shared, just not my personal status. How do I stop that from happening? Ta