A game can be technically undecided long after one player has stopped believing in it.

A contest can remain mathematically open long after one person has stopped believing. The score says undecided, the possibility is real, and the internal surrender has already happened, which is why comebacks are so often described as psychological. Belief is a component of the position, not a commentary on it.

When you notice yourself conceding early, check the actual situation rather than the feeling. Ask what would have to be true for it to still be possible, and whether it is. Often it is. And when someone near you has given up on something not yet lost, describing the real position plainly is usually more helpful than encouragement.