fortune cookie help!
The person who is courteous to others will gain friends. If someone is always grumpy or discourteous, they won't have friends.
While it may seem an outdated thing, people who are friendly and courteous to others (including respecting their feelings) will have more friends.
A simple hello with a smile on your face will usually be returned in like manner. You draw more bees with honey than vinegar as the old saying goes. You wouldn't want to be friends with a discourteous person. So your fortune cookie is telling you that in order to make friends you must be nice.