A clown without a circus is just a man with an oddly-painted face and over-large shoes.
A priest without a congregation is just a gentleman talking to himself in a big chilly building.
And a waitress without customers is just a woman with an apron, notepad and pencil.
One way or another, most people's lives have purpose when they interact with others. Feeling a sense of purpose can help you believe that you're living a life of meaning. For some this can be a profoundly life-changing mission, but there's just as much potential reward to be had from being a parent or through working at a job which gives you a sense of achievement at the end of the day.
This is fine in theory of course, but what happens when your mood has taken a nose-dive? It's at times like these when, far from feeling you have a sense of purpose, just about everything can seem meaningless.
So how exactly do you tackle this meaning-deficit?
Think, perhaps, of a piggy bank into which you drop just a few small coins now and then. Sooner or later it will be heavy with cash, but it rattles hollowly to begin with. You need to start somewhere however, and perhaps the same applies when it comes to seeking meaning in life?
When your tank is low, the smallest shared interaction can help. Remarkable as it may seem, and even if you need to force them out, a smile and a hello to a stranger - a shop assistant or receptionist for instance - can be like pennies in the belly of your meaning piggy bank. Stroking someone's dog (best, perhaps, to stick to small ones if you don't know them) can remind you that your world has more than one species.
If you want to be part of something bigger, it often pays to start by thinking small.