How about getting hold of a few sticks of chalk, and writing inspirational quotes on the pavement?
Or pack up your evening meal, and go and eat it in the park? I know it's cold outside, but as long as it isn't raining you can wrap up warm. If it is just too cold outside, then sit in the car and look out at a nice view.
Send a message in a bottle.
Write an inspirational message in a pretty card, and leave in under the windscreen wiper of a random car.
Put a romantic note in your husbands packed lunch.
Put a silly joke in your child's packed lunch.