We have two regular delivery drivers deliver to where I work. Now, I accept that it's not the most exciting job and it must be annoying when you have to wait for someone to tell you where to put things etc,
One of the men always has a cheerful good morning and something to say about last night's football, the weather, how busy he/we are.
The other barely speaks unless he has something to moan about - like us keeping him waiting! Please, you spend an awful lot of your life working, you'd enjoy it so much more if you smiled a bit. And we'd be happier to see you, which might make your life a bit better too.