别灰心，以后还有很多晋升机会。

Don't ___lose ___heart; there'll be plenty more chances for promotion.

我们必须学会应对挫折，不要丧失信心。

We must learn to deal with setbacks and not ___lose ___heart.

即使在几次实验失败后，这位科学家也拒绝放弃希望。

Even after several failed experiments, the scientist refused to ___lose ___heart.