Sometimes it's an effort but I force myself out for a walk somewhere where there is greenery, fields, trees, by a river or at a beach, and away from traffic. I feel better afterwards.
I did it today. People said 'Hi'...I saw a heron and a teenage boy asked what it was so we had a chat about herons...I saw a mother duck with 7 tiny ducklings... stroked a couple of dogs...found a lane to explore at another time. And decided to get a folding bike as the whole area is flat and traffic free. I enjoyed it all and the sunshine was lovely.
On cold, wet days I would go to a bookshop and then I'm in a different world browsing through the books. Or read at home and treat myself to something nice to eat. I would also eat out or go for a coffee and cake usually at a garden centre where the plants and flowers cheer me up.
I often go through the local paper and note down exhibitions, dog shows, flower shows, fairs or fetes, open days, coffee mornings, films at the cinema, evening talks etc...in my diary. Things to look forward to.