Do some breathing exercises.
Dress in your comfiest clothes.
Stand up and stretch for a few minutes.
Listen to any happy voicemails you have.
Take a hot bath/shower. Take an extra 5 minutes than usual.
Have a cup of tea, coffee, or hot cocoa.
Cuddle your favorite stuffed toy.
Make a list of movies you want to watch.
Stick post-its with positive affirmations around your house.
Think of your happiest/funniest memory.
Clean your jewelry and/or moisturize your tattoos.
Watch your favorite childhood movie.
Watch your favorite television show.
Youtube videos of others laughing ridiculously.
Take your dog for a walk.
Go for a walk without your dog.
Play with your cats/other pets.
Clean out your closet. Put out of season clothes in storage.
Learn to cook a new meal.
Improve your skills at a task you can already do.
Give yourself a massage or have someone else.
Declutter your surroundings.
Take an hour (or a full day) just for yourself.
Curl up in a big blanket.
Do a word search, sudoku puzzle, crossword, etc.
Interact with others. If nothing else, ask a cashier how they are.
Fill a notebook with positive quotes/coping skills.
Complete one five-minute chore.
Stay away from mood-altering substances.
Clean out your computer/email/phone/etc.
Color something or draw without thinking.
Send a loving message to someone.
Sing/dance along to an upbeat song.
Step outside and get some fresh air.
Take photographs of/doodle nature.
Dress up and take selfies.
Take a break from your computer and phone.
Fill a box with your favorite things.