This quote means that friendships and credit are strongest when they are not taken advantage of. It’s like having a bank account with a lot of money saved up; you want to keep saving it and not take it out for anything unless it’s really necessary. Likewise, if you never rely on a friend for anything, you preserve the friendship and maintain the trust. While using a friendship or credit for good intentions can strengthen the connection, taking too much can leave both credit and friendship depleted or even destroyed.