活在当下是一种珍贵的境界，让我们能够充分体验生命的美好，以下是一些精选的句子，用英文表达：

1. 'The present moment is the only moment available to us, and it is the door to all moments.' - Thich Nhat Hanh

2. 'The secret of health for both mind and body is not to mourn for the past, worry about the future, or anticipate troubles, but to live in the present moment wisely and earnestly.' - Buddha

3. 'Yesterday is gone. Tomorrow has not yet come. We have only today. Let us begin.' - Mother Teresa

4. 'The future is something which everyone reaches at the rate of sixty minutes an hour, whatever he does, whoever he is.' - C.S Lewis

5. 'The best thing about the future is that it comes one day at a time.' - Abraham Lincoln

这些句子提醒我们要珍惜当下，不要被过去或未来所困扰，而是要将注意力集中在眼前，用心体验每一个瞬间的美好。