It's expected that you go to your friend's birthday parties.
Today is Ton'y best friends birthday, and he has been invited to their birthday party.
Tony is tired and wants to catch up on rest.
Tony let's his friend know how exhausted he is, and shows up to the party to drop a gift off and wish him a happy birthday before going back home.
Tony ignores his best friends calls and doesn't go to the party.
Tony's friend invites him out for drinks the next weekend, so they can make up for time lost at the birthday party.
Tony's friend stops hanging out with him as often, and fails to show up to Tony's birthday later that year.