Anxiety is a normal, healthy human emotion. It comes in for a lot of stick these days, but everyone suffers from it at one time or another and it has evolved for a number of very good reasons.

First and foremost, anxiety keeps you safe. It alerts you to potential dangers, makes you better at threat perception, and discourages you from taking unnecessary risks. It encourages you to think of alternatives, prepare backup plans and expect the unexpected. Indeed, those who experience anxiety tend to be better prepared, and cope better when things go wrong, than those who don’t.

Anxiety can also push you to be better. If you’re anxious about an exam, you study really hard so that you ace it. If you’re anxious about giving a speech, you practice so much you deliver it like a seasoned pro.

Even social anxiety has its benefits. Worrying what people think of you, how to make a good impression, and not hurting their feelings actually makes you a nicer, kinder, more empathetic person who cares about and tolerates the thoughts and opinions of others. Consequently, you tend to be better liked than those who don’t worry how they’re seen.

All of which shows that anxiety is not something negative. Excessive anxiety, on the other hand – that’s a different kettle of fish altogether.

Autism and anxiety go together like syrup and waffles. I’m not going to talk about the anxieties Aspies suffer from altered routines, sudden change, sensory issues, societal expectations or social situations as these are well-known and extensively covered elsewhere. Instead, I’m going to address something surprisingly common but rarely discussed: the general, non-specific, all-pervading anxiety that all is not well with the world.

It’s a feeling that comes and goes, sometimes with identifiable triggers and sometimes not. Probably the most common time I’ve heard it affecting people on the spectrum, myself included, is after moving house. While it’s popularly said that depression comes from dwelling on the past and anxiety from dwelling on the future, this does not hold true for the anxiety I’m talking about, for it exists in the present moment and no amount of rationalising or reasoning can remove it.

I’ll give you an example. About ten years ago I moved into a block of flats. My flat was on the third floor and contained all my belongings. I had a sea view, an allocated parking space, an entry phone system and a concierge. I had my support workers coming in regularly, and kept up the same routine as I had in the previous place. I had everything I needed to feel safe and happy. So why did I spend two weeks curled in a ball on the floor whenever I had a spare moment?

I was terrified, but I couldn’t work out why. The door was locked and nobody could get in. I was on the third floor, so totally safe. I had working smoke detectors and my car was right beneath my window. I had my own curtains and bedsheets, my model, my Jeffery Deaver books and my Starsky and Hutch DVD boxset. I had my guitars, my phone, the internet. I had food, an oven, a washing machine. There was no reason I should feel anxious.

But I did. I was anxious all the time, only without an obvious cause. Despite knowing I was safe, having all the things that I needed to feel comfortable, and having support workers  come in, I had an ever-present feeling that everything was wrong. It’s not something you can think away. There’s nothing you can do to get rid of it. And nor can you distract yourself – this type of non-specific anxiety pervades your very being. It’s there when you wake up and when you go to sleep. It’s there even when you refuse to think.

I’ve known others who, after moving house, take months to finally settle and feel comfortable. Why do we feel this way? Who knows. It happens to me every time I move, even though I’ve lived in sixteen places. The same books in the same order on the same bookcase in a different house fills me with anxiety, and there is nothing to alleviate the dread.

I felt the same non-specific anxiety all day yesterday and most of today. So did my wife, who’s also on the spectrum. We’re going on holiday tomorrow and so we’re both anxious about that – the change of routine, fear of the unknown, and so forth – but this was not that. This was, again, the sense, the dread, that something was very wrong with the world, but we couldn’t really say what.

I think it was because we packed on Saturday, leaving Sunday and Monday to relax. Trouble was, neither of us could. Can’t start a new book because I’ve got one for holiday. Can’t write my novel because I’ve got to a convenient break. Can’t pack my hand luggage until the last minute. Everything felt wrong. Doing the same things – getting the kids up, getting them dressed, taking them to ballet – it all felt wrong. We couldn’t get comfortable, couldn’t relax, so anxious we couldn’t even distract ourselves from it.

I’ve spent two days pacing from room to room. Picking up the guitar, strumming for thirty seconds, putting it down. Flapping my hands. Trying to watch TV. Tidying the kitchen, the lounge, the playroom. It all feels wrong.

Let me be clear – I’m not particularly anxious about going on holiday tomorrow. My anxiety was all about the here and now. And how do you get rid of that? I’ve already dealt with my anxiety about the holiday by planning in detail, making backup plans, writing lists, checking and double-checking and triple-checking everything. The anxiety I’ve felt hanging around the house the last two days, walking the dog, going to town – it comes from somewhere else, somewhere I can’t clearly identify. It’s a horrible feeling that makes me want to cry, and sometimes I feel my chest constricting and my heart pounding away, and because it comes from nowhere, because there are no thoughts to challenge or problems to prepare for, there’s nothing you can do but endure it.

That’s what I mean by non-specific anxiety. As I said, sometimes it has an identifiable trigger – moving house, the days before holiday – but sometimes it’s just there, anxiety that serves no purpose and drives you out of your mind. So you learn to live with it and hope that, soon enough, you can stop feeling so afraid.