Al-Uthaymeen: If you Don't Give Thanks...

The favour of security - if you don't give thanks for it, it will be replaced with fear. 

The favour of provisions - if you don't give thanks for it, it will be replaced with hunger. 

Likewise, the favour of religion - if you don't give thanks for it, it will be replaced with Kufr.

-Shaykh Muhammad bin Saaleh al-Uthaymeen (may Allah have Mercy on him)