Go to a local race or marathon and cheer the people running, particularly those that look exhausted and in need of some moral support.
Write to your favourite author, or the author of a book you really enjoyed, and tell them how good their writing is.
Make a playlist of songs that remind you of a time you spent with someone, then give them the "tape".
Plan a treasure hunt for kids - or adults! We hide Easter eggs around the office without telling people to see how long it takes them to realise 😂.
... but not for yourself. Plan a day trip, weekend away or (if you are feeling brave) a holiday for someone else.