What a nice idea #NationalComplimentDay is, especially on Twitter. The world is full of short-tempered people, angry at things they read or hear, or that their day hasn't gone well. What better way to spread a little sweetness and light?

According to holidaycalendar.com, National Compliment Day is designed to encourage you to 'say something nice to your friends, family, and co-workers'. It might come a bit awkwardly for a reserved Brit, but it's worth making the effort – it's surprising how much one's mood can be lifted by a well-timed word of kindness.

And it is, after all, quite biblical. Holidaycalendar again: 'Studies have shown that giving out compliments also has a beneficial effect on the person giving out the compliment.' What studies these are we are not told, but there's no need to be too suspicious: after all, Jesus said it is 'more blessed to give than to receive' (Acts 20:35). It's sound psychology as well as sound theology. It might be for something we do purely routinely, but it's nice to have it noticed.

There are even Bible proverbs about it: 'A generous man will prosper; he who refreshes others will himself be refreshed' (11:25); 'An anxious heart weighs a man down, but a kind word cheers him up' (12:25). There isn't nearly enough kindness around.

Paying compliments to your friends, family and co-workers, though, is – in the normal way of things, unless you've had a terrible row – the easy bit. They are people for whom we feel affection and loyalty. If we don't compliment them, it's because we're forgetful.

But what about the people we dislike – hate, even? Sometimes it's just a clash of personalities; sometimes we have suffered real injuries. And while we might get to choose our friends, we don't get to choose our families – or even, by and large, our co-workers. Some of those enemies might be among those closest to us.

Jesus, of course, said something about that too: 'You have heard that it was said, "Love your neighbour and hate your enemy." But I tell you: "Love your enemies and pray for those who persecute you, that you may be sons of your Father in heaven."'

As ever, the Christian message leaves us uncomfortable. It's easy to do what everyone else does; much harder to go against the grain of humanity and do what doesn't come naturally.

#NationalComplimentDay is a good idea; but maybe 'nice' isn't the word.

Follow Mark Woods on Twitter: @RevMarkWoods