Definitely try and get out for a walk at lunchtime if you work from home or are in an office.
When I used to be based in Ripon I’d wander along the river and chat to the same old boys who were fishing about how their day had gone and what they’d caught. That led to some great ‘…the ones that got away stories’ including the hunt for the big pike in the canal.
Buy a Big Issue when you see a seller then chat to them and ask them how there day has been.
Make an effort to contact an old friend you’ve not heard from for a while.
Bring your neighbours bins in one day.
If you a kid(s) at school or college who are doing well or enjoying it email their teacher and thank them for their hard work. I did that last week and my daughter said her teacher almost cried when she read my email as she’d been having a bad day.