Why are you so afraid to laugh?

I know we live in serious times, life is full of uncertainty, there are a lot of things going on to worry about.  Not just in your business or your workplace but in the world in general.  I hear it so often, "I need to convey a professional image, I can't go around with a smile on my face".  WHAT???????????
Since when does being surly compute to success?  I come across a lot of folks in business who are afraid to laugh, smile, tell a joke or spread some happiness all in the name of being professional.
I grew up with the idea that having a good sense of humour and being able to laugh at yourself is one of the greatest virtues. 
Do you really think you are serving your clients and your employees better by being serious all the time?  Some of the most successful and enjoyable companies I have been associated with are the ones where the leaders lead with humour and a smile.  I am not saying that you need to go around laughing all day long, however you do need to lighten up if you are guilty of being serious all the time.
I know people who work in some grim businesses such as Funeral Homes and with people who are dying and they have the greatest senses of humour.  They have learned that there success and survival depends on them being able to find humour in life's toughest jobs.  If these folks can have a laugh can't you?  Are you dealing in such a grim business that you can't lighten up a bit?
There is an old saying, not sure where it came from, "If you are light in your life it is easy for others to lift you up and help you along the way!"
Go ahead smile, make your day.