Philosophy questions apart (like the article), for most normal people when you encounter the phrase "I'm too busy" 9 out of 10 times it just means "I don't want to do whatever you are proposing but don't want to tell you that to your face". It could be only half a lie though, like they could be busy in general and the proposal you gave them is in their "relax time" so they are too busy actually relaxing to do it. Or they could have all the time in the world and still say that.