This is good luck charm(お守り）
The word（お守り） "omamori" literally means "to protect.
Since this is the season for entrance examinations,
many parents are buying good luck charms for their children at shrines.
My child will be taking an entrance exam next year, will I really buy it?maybe~
「自分を信じで頑張ってね」means 「Believe in yourself and good luck.」