It is quite extraordinary to feel so happy, so proud and so profoundly sad, all at the same time.

I’ve just completed the first draft of a book. One hundred and twelve pages. My story of nearly thirty years in consulting, the lessons I’ve learned, the mistakes I’ve made, the people I’ve worked with and the things I hope might be useful to others.

There is still an enormous amount of work to do. It needs editing, restructuring, checking and probably a fair amount of ruthless cutting. But it exists. One hundred and twelve pages that didn’t exist a few days ago. I’ve set myself a challenge, I’ve made real progress, and for the first time in a while, I have a substantial project that excites me.

I’m happy. I’m proud of myself. I may be unhappy with it tomorrow, but today I’m happy, and I’ll take that.

And yet, at precisely the same time, I’m profoundly sad.

I’m sad because I feel that PSP is progressing at a frightening speed. My days have become a roller coaster of extraordinary highs and devastating lows. There are moments when I can think clearly, dictate thousands of words and feel almost like my old self. And then, sometimes without warning, I can barely communicate at all.

There are the dreadful episodes of freezing and powering down. The enormous sensitivity to light and noise, to the point where even ordinary household sounds can become unbearable. The behavioural changes that I recognise but cannot always control. The constipation and other stomach problems that have recently turned some of my nights into battles I would rather not describe. And a growing collection of other symptoms, each apparently determined not to be left out.

In between, there are moments of calm. But increasingly, those moments seem to be getting shorter and further apart.

Perhaps I’m imagining it. Perhaps the progression isn’t as rapid as it feels. PSP has taught me repeatedly that a terrible day doesn’t necessarily mean an equally terrible tomorrow. I’ve written about that unpredictability often enough.

But right now, I feel as though PSP is gaining on me.

My mind is still there. My ability to think, reason, reflect and put words together is clearly still there. I’ve just written a staggering amount in a remarkably short time. Admittedly, I’ve had nearly thirty years to accumulate the stories and lessons, so it’s not quite as though I’ve invented everything from scratch.

But I’ve also developed a sense of urgency that I cannot entirely explain away.

And I’m not just talking about the bathroom.

The strange thing is that I don’t want to feel this urgency. I want to take my time with the book. I want to enjoy writing it, put it aside for a few days, return to it with fresh eyes, argue with myself about the structure, rewrite the weaker sections and eventually produce something that I can genuinely be proud to publish.

I want the luxury of not having to hurry.

But another part of me is saying something quite different. Keep going. Write while you can. Don’t assume that the ability to communicate so freely today will necessarily be there tomorrow.

That is a difficult voice to ignore when you’ve spent the day experiencing both extraordinary productivity and moments of almost complete helplessness.

I don’t know whether that voice is wisdom, fear or simply the inevitable consequence of living with a progressive disease. Probably a combination of all three.

And I certainly don’t want to turn this into a self-fulfilling prophecy. I hope and pray that I have a long time ahead of me. I hope that I can spend weeks, months or longer working on this book, enjoying the process and making it better. I hope I look back on this extraordinary burst of activity and wonder why on earth I thought I needed to rush.

Nothing would make me happier than to discover that my sense of urgency was completely unnecessary.

But I cannot pretend that I don’t feel it.

Perhaps that is what makes today so emotionally confusing. The book represents something wonderfully positive. A sense of purpose, achievement, creativity and the reassurance that I still have something valuable to contribute. It has reminded me of a part of myself that PSP has not taken away.

At the same time, the speed at which I’m writing it reflects a fear that PSP might eventually take away the very ability that makes writing possible.

Both feelings are real. Neither diminishes the other.

So today I’m allowing myself to be proud. Really proud. One hundred and twelve pages is one hundred and twelve pages, and I’ve earned the right to enjoy that achievement.

But I’m also allowing myself to be sad.

I’m proud of what I’ve written. I’m happy with what I’ve produced so far. I’m sad about the reason I feel such urgency to finish it.

I desperately hope I’m rushing for no reason at all.