A fisherman had been fishing for along time but without luck. At  last he tugged at his net and saw a small fish caught in it. "Please let me go," Begged the fish, "I will grow bigger in a few days and  then you can catch me again." The fisherman said, "Now that I have caught you I won't let you go. if I  leave you, I may never see you again." 
A bird in hand is worth two in bush. 