Go outside
Obviously, stay away from other people. Only actually exercise. Walking counts. But please don't start sunbathing in little groups with a BBQ and a Bluetooth speaker and then tell the police I said you could do it. But do go outside. It's good for you. The air is good for you. The sunlight is good for you. Trust the British weather to suddenly go really quite nice the moment we have to stay inside. It's wonderfully ironic and given our love of irony, I am sure we can all appreciate it. Outside, whilst walking 2m away from anyone not in our household for at least 30 minutes per day.
I cannot stress this one enough. I know people keep going on about it, but it really can change your mood. It'll also help with temperature regulation, give your muscles something to do that isn't changing the channel or scrolling through Instagram, and there are LOADS of dogs around. You shouldn't go and pet them because #socialdistancing, but you can look at them and they're normally really happy and cute. If you have a dog at home, take it outside so other people can look at him or her. Your dog also needs to walk, but if you have a dog you knew that already.
Go easy on yourself
Twitter is helpfully full of accounts telling us that Shakespeare wrote King Lear whilst in quarantine, Isaac Newton began to come up with his theory of gravity and so on. This is not helpful. We are in the middle of a pandemic. It is okay not to be productive. If you have ideas and things you want to accomplish or write (look at me, I'm writing a whole blogpost. In the lockdowns of the future, I hope to be an example to many) or read, go for it. I really want to learn Ancient Greek. I've not started yet, but I keep saying I will. If you fancy picking up drawing or learning to code then great. If not, or you lack motivation or whatever, then that's really okay too. It does not matter if whenever this is all over you are the same basically mediocre person with no new skills or talents. Don't beat yourself up. Just look after yourself, try and eat three meals a day and keep yourself entertained. It does not need to be groundbreaking or revolutionary. Developing a new skill or writing a novel (or the next King Lear, of course) is a great way to pass the time but then again so are series 1-5 of Mad Men, 1-10 of Friends and 1-6 of Brooklyn 99, which are all on Netflix right now. Sitting in your room for a few hours and watching TV or rereading your favourite books or doodling or whatever it is that you do that you probably think is not productive is perfectly acceptable.
This is not the time to convince yourself that if you haven't read Plato's complete works, written 32 new plays, learnt French and Russian and run a marathon in your back garden by the time this is over, you've somehow wasted this time and are a bad person.
Find structure where you can
Most of us have nothing to do. Or nothing pressing to do. Things can be put off, we aren't in work or study and there's just a lot of empty space on our calendars. Having said all that, there are still things we must do. We need to eat. We need to wake up. We need to go outside (see above). We also need social contact (video chat, please). So eat three meals a day at vaguely the same times. Go outside around the same time. If you enjoy reading, set aside time for it and if you can, try and stick to it. Organise video chats and skype calls. Talk on the phone with your grandparents if they are still alive at the same time (they'll appreciate the consistency and contact, as well). If you can say, right, I am going to wake up at 9am or 8am or 6am every day and eat breakfast 30 minutes later, lunch at 1pm, walk at 4pm, phone grandma at 6pm and so on, it'll help your day so much. It won't feel so much like a black-nothingness. There will be things to look forward to. And if there are things to look forward to, you'll be more motivated to do them and keep doing them. And add more things to do.
Eat properly
This is good advice generally, but even more so now. Try try try and try again to eat regularly and properly. Good meals will help. If you can cook, cook for yourself. It will fill time. If you can't cook, now is a good time to learn (though, no pressure, see above) but still, try and eat properly and regularly. Fresh fruit and vegetables. Etc.
Treat yourself
Finally, treat yourself. This is a bloody hard time for everyone. We are stuck inside. We don't know when it is going to end. We can't see our loved ones, we can't hug our grandparents and many of us have family and friends working tirelessly for the NHS and other key services, and we're worried about them. We deserve a treat. Regularly. Because, if we are complying with the guidance, and going outside only when we need to and social distancing when we do, then we are doing our bit. And our bit is hard. Yes, it's not hard like working for the NHS is hard. Or being a police officer trying to understand the new regulations. But it is still hard, and it will take its toll. So loads of treats are necessary. Anything you like. Enjoy it. Believe me, you deserve it.
Things will get better. People will stop dying and soon we will go outside again and have BBQs and all talk about that time we had to stay inside for weeks without any sign of it improving. We will get married and have parties and move into new homes and make new memories with family and friends. We will see our grandparents again and hug them and love them in close proximity rather than from afar. Friends will be in our rooms physically, rather than as images on a screen. We can go on dates and to restaurants and, yes, shock-horror, we will be able to go back to work and study. And we will all be so grateful for it. But for now, it's difficult and the light at the end of the tunnel is at best very faint. We will get there, we just need to keep going. So look after yourselves, treat yourselves, smile and be happy. We can do this.