What goes up must come down, said Isaac Newton. Oh, how well he knows my mood. Sometimes I am so keyed up I feel like I’m dancing across clouds, but at the same time I have this lurking knowledge that within a few hours I will feel like crying into a large glass of wine.

Perhaps it’s just that by experiencing this amazing high, a low (however minor) feels a hundred times worse than it would usually. That’s why, even when I experience elation, I have to almost deliberately tone it down, to try to ease the extremities.

An example. This morning, I woke up happy. The sky was cloudless, the perfect clear blue of a sapphire. I plugged myself into my favourite playlist, and almost skipped along the pavement to the train station.

As the train pulled in at Waterloo, I felt like an observer. I stood still, and watched hundreds of people scurry past me like ants, all intent on their own path. I looked up to the ceiling, taking in the beautiful architecture, the iron beams and the huge clocks. It was one of those moments in life where you stop participating, and just watch the world.

I found it amazing, mind-boggling, that each of these people was on their way somewhere, to interact with tens of other people. Each person had a family, friends, a job, a life. The webs of each life would spread around the world, in a million different offshoots and connections. The enormity of that left me momentarily dumbstruck.

Heading up towards Waterloo bridge, I was almost dancing. The icy wind smacked my face, and it felt fantastic. I could see cyclists getting battered to-and-fro, struggling to push against the gale force. Yet, to me, the wind felt exhilarating, refreshing.

That was when it hit me. “Tone it down, girl” I told myself sternly. “Too happy now and you’ll be in tears by lunchtime.”

Yet despite all my experiences telling me that this was true, I didn’t want to believe it. Why would I voluntarily spoil my own happiness?

Well, perhaps I should have listened to myself more carefully. What goes up must come down.