The last few months have been awful for so many people, with millions dealing with grief, stress, financial difficulties, job losses and isolation caused by the pandemic.
Now, a new lockdown in England and similar restrictions across Scotland, Wales and Northern Ireland are adding to the gloom of winter - a season that can be tough for many people even in normal times. But the country's leading mental health experts say there are things that many of us can do to give ourselves a lift. Here are some of their tips.
Getting outdoors for exercise can be difficult in winter, but pretty much all experts agree that it's a great way to boost your mood. "Our minds and bodies are completely inseparable", says Dr Brendon Stubbs, of King's College London.
Exercise triggers the release of endorphins into the bloodstream, relieving pain and producing a feeling of well-being. Research by Dr Stubbs has also shown that exercise also increases electrical activity in the emotional processing areas of the brain, particularly the hippocampus and the pre-frontal cortex.
"It's vital to keep active to improve your mental health and stimulate your brain including those areas", he says. "If you don't exercise, the activity drops." That's one of the reasons why a lack of exercise increases your risk of anxiety and depression.
Exercise can also boost the production of a protein, BDNF, or brain derived neurotrophic factor, which is crucial for brain health.
"You can think of it as a kind of brain fertiliser - it helps parts of your brain regenerate," says Dr Stubbs. Even short periods of exercise - just 10 minutes - can help. "Anything that leaves you slightly out of breath, like a brisk walk, or something like gardening, or a cycle ride, will do."
Adopting helpful habits to stop you over-thinking is one of the best things you can do, says psychologist Prof Jennifer Wild of Oxford University. She calls it "getting out of your head."
People often dwell on problems, going over and over the same negative thoughts, and Prof Wild has some simple suggestions to stop that happening. "If you've been worrying about a problem for 30 minutes or more without coming up with a plan of action, or you've been going over questions with no answers, it's time to stop", she says.
The main thing is to shift your focus from worries to practical problem-solving. So stop and ask yourself what steps you can take to address the problem. It's not easy, of course, to stop yourself dwelling on problems. Some recommend physical activity to help you shift mental gears. In any case, it takes some training.
It's perfectly normal to worry, but many of our worries never materialise. One study of patients with anxiety found only around one in 10 worries ever turn out to be real problems. One explanation is the way we have evolved. It has made us highly tuned to negativity and danger, as a defence against threats which led to death or serious injury.
Danger is "over-encoded in our brains", says Prof Wild. "You can make yourself feel much calmer if you recognise that you're over-thinking, stop and focus on facts."
Set a new target
"Setting a new goal or target, can really help pull you through," says Cardiff neuroscientist, Dr Dean Burnett. That could be a big project like learning a language or something as small as trying out a new recipe. If big ideas are too much, start small.
The point is that if it's outside your comfort zone, and it's pushing you forward, it gives you a focus and a sense of control. For many people that's hugely helpful for their mental state. "Novelty is fundamentally rewarding," says Dr Burnett.
"Learning to do new things is frequently how we acquire self-worth", he adds. "Goal-motivated behaviour is one of the most fundamental ways that we operate."
Talk it over
Covid-19 has made it a lot harder to be with others in person, and winter can make it harder still. That's a big issue for millions of people and the mental health consequences for some will be serious. So it's a good idea to maximise the little social contact that is available.
"We're not really designed to be on our own," says Prof Emerita Elizabeth Kuipers, of King's College London. "We're socially-oriented. We feel better with social contact." Talking problems over when you can is a good idea, but the key thing is how it's done, she says.
"Going over problems again and again, just rehearsing how terrible you feel, may not help at all. Talking things through with someone who can help you reframe your problems, and help you move through them can be much more helpful."
Isolated people are more likely to focus on themselves, says Prof Kuipers, and that can make things worse. So reach out when you can, and if Covid-19 means you can't do that in person, make that phone call to a friend, or arrange to talk online.
Do it badly
Optimists live longer, have better relationships and better immune systems, says Olivia Remes of Cambridge University. And the good news is you can cultivate optimism: an inner sense that you can make a difference to your life, and that it's not all down to things outside your control. How? Her number one tip is the principle of "do it badly".
In other words don't wait to do things perfectly at the right time on the right day. That's even more important in winter when gloomy weather might make you think twice about doing something.
"Our inner voice of criticism continually stops us from doing worthwhile things", she says. "Jump straight into action. Do things and accept that they might initially be done badly. When you do that, most of the time the results are actually not that bad - and they're almost always better than doing nothing."
Olivia's other tips include writing down three things each day that you're grateful about, to force yourself to focus on what's gone well and why. It'll fire up the left hand side of your brain which is associated with positivity.
"Emotions are contagious", she says, so "if you can, gently steer away from negative, miserable people who are constantly complaining", because you'll find yourself becoming one of those people too.
Illustrations by Gerry Fletcher