Better Be...
"Better be" implies that something must be a certain way, or else there will be negative consequences. It's a strong warning or imperative, often used in informal language. The phrase means "You should definitely do this" or "You have to do this," and not doing so will lead to trouble. Link
Sometimes we think something will happen in a certain way but we might be wrong. We cannot predict the future, we cannot tell the outcome of events, we can only wish things turn out well in our favor.
Better be is a definition of how something ought to be, but it's not always like that.
Better be can be optimistic too
There is certainly a good way to look at it.