Be thankful, gracias la vida!
Remind yourself of all the good things in your life.
You have won the lottery being born in the UK in the 21st century already!
Think of your life if you lived in in Sudan, Ukraine, Russia or Venezuela.
After that, look for periods of happy moments, kindnesses, content or delight. Just moments, that's all you can expect.
Find a purpose, something that adds good to the world preferably. Look nearby, a lonely neighbour, an unloved patch of ground, a brownies group.... can you help?
Let go of all forms of worry or anxiety - your body, your health, your life, your family etc etc.... just let the worries come and then let go of them! Like balloons floating away...
Makes some plans to give yourself something nice to look forward to.
Finally, get a good book to read.
And - most important - get to bed at a decent time and make sure you rest enough.