俗话说：赠人玫瑰，手有余香。你有没有遇到过这类情况：一个素未谋面的陌生人前来帮忙，却不求回报；一位咖啡店员出于好心而免费给你一杯咖啡…这些平日里看似不经意的好人好事可能会改变人们一天的心情。有些善举可能无足轻重，但有些则可能救人于生命之危。

It could happen anywhere at any time. It's often unexpected, but almost never unappreciated. Most people, at one time or another, have been on the receiving end of a random act of kindness - that moment of pure altruism when a complete stranger stops to offer aid, generosity or compassion. You may even be in a moment of dire need. In a sometimes callous world where people can be so focused on what they're doing, a random act of kindness can make all the difference.

They can be relatively insignificant. Hannah Bailey from London, for example, told the Metro newspaper about how she was given her fruit and vegetable shopping for free. The seller did her a kindness when it emerged she didn't have any change to pay. She was happy about it all day.

The city of Naples has long had a tradition called 'caffè sospeso'. When buying coffee, a person who has recently been lucky would purchase two cups but only drink one, leaving the second one anonymously, out of the goodness of their heart, for a poor person to  claim for free. This tradition is now more common worldwide.

However, in some cases, these little acts can be a matter of life and death. Take, for example, the unnamed commuter, who in June 2018 fell off a station platform onto an electric railway track in Toronto, Canada. A quick-thinking, but even now unknown, bystander selflessly leapt down to pull him to safety.

Or Jonny Benjamin, who in London in 2008 was persuaded not to commit suicide by a passer-by. He had been considering jumping from a bridge. He later found the Good Samaritan and thanked him.He may one day find a way to pay him back in kind – though that's not the point.

So, why do it? Often, the acts aren't reciprocated. The people never meet again. According to UK charity The Mental Health Foundation, acts like these can "give our lives new purpose, show us other perspectives on our own problems and even make us feel euphoric."

So give it a try. Hold open a door for someone, deliver a compliment - even give up your seat on a bus. Help someone who is in need. It takes all kinds. It needn't be anything huge. One day, whether you need it or not, someone might help you in your hour of need.