Think about it. A friendship is like a piggy bank. Doing something nice for someone, such as sharing your lunch, would being like putting a quarter in a piggy bank. This is called a deposit.

Doing something mean such as arguing is like taking money out. This is called a withdrawal. Most interactions with people are either deposits or withdrawals.

For someone to be your friend you need to have made a lot of friendly deposits. If you make too many withdrawals by not being nice, the person won't want to be your friend.