The question of predestination is one of an intricacy disproportionate to its interest, to paraphrase Chief Justice John Marshall, or at least its relevance to us on earth in leading our lives (interesting phrase, by the way: leading a life instead of, say, living it).
What I mean is that we cannot be so sure of the answer — so sure about whether or not our eternity is predestined so that our efforts here on earth don’t matter — that it would make rational a failure to try our best to act as God would want. If asked whether one believes in predestination, it is bad advice to say other than, “I can give you my opinion of what the Bible means, but I can’t be 100 percent certain, and my opinion will in any event not tell you that you should not act as God says we should act elsewhere in scripture.”
The calculus here is very similar to Pascal’s wager, is it not? You have, again, four possible quadrants/outcomes, and acting as if there is no predestination can have a huge payoff and avoid a huge loss, with relatively little opportunity cost compared to acting as if there is predestination.
This is true elsewhere in the Bible, by the way. That is, it can be foolish to rely too much, if we don’t have to, on what can only be an uncertain interpretation of the text — and the less of the text there is, the more foolish the reliance.