Jesus never promised His disciples an easy time. Quite the opposite; it may be hard, but they must not be deterred by opposition (Matthew 10:22).  One day, the Lord will finally vindicate His people (2 Thessalonians 1:6-7).  In the meantime, even when they are enduring hardships and persecution, their suffering is known to God.  Because He cares for them they should not be afraid (Isaiah 41:10).
 
Jesus used the illustration of sparrows, little birds which were trapped and sold for food.  Poor people might buy two of them for a very small amount, or five at a discounted price (Luke 12:6-7).  Jesus did not comment on the morality of that style of trading; He said that Father God knows every time a bird is trapped, and that none loses its life without His knowledge.  They are not just flocks of anonymous creatures, but each one is known and treasured by God.  Although death will come to each sparrow in one way or another, God cares for each one until that time comes.
 
God's knowledge is so detailed that He knows the number of hairs on every head.  Nothing escapes His notice; as the Creator, He keeps a constant check on all He has made.  It is because He cares so passionately about all He has made (Psalm 145:9).  The disciples needed to learn that when they were sent out without any resources except Jesus' powerful authority (Matthew 10:9-10), they were highly valued and would never be abandoned.  Even when persecution ended in death, they should not fear, but trust that God still held them preciously (Acts 7:54-60).
 
It is right for us to look after ourselves as best we can, but it is wrong to assume that we can be our own ultimate protector.  That responsibility is in God's hands alone; and He honours His promise to safeguard His people.  There will be a time to die, but even that date and the accompanying circumstances are held in the Lord's loving hand.  Our responsibility is to continue worshipping and witnessing until He calls us home.  Fear will only spoil us and frustrate His purposes; it will impair our worship and impede our witness.  So do not be afraid; you are far more valuable to God than you have ever imagined.