Here are five easy things that can help you. They help me feel better when I'm upset.
Breath. It may seem like a simple thing, but taking a deep breath sometimes can help improve your mood.
See the sun. Don't be a vampire. Go outside. Have fun. Being outside can help give you a positive look on the outdoors. It also makes sure you get vitamin D.
Put down the screens every once and a while. Being on a screen all day can make it hard to sleep.
Find something that you like to do, and do it. For me, it's Legos and school. Find something to keep your mind off stress and issues.
The last thing I have for you, is get enough sleep. Enough sleep where your not tired all day, but your not late for your day.
I think doing all of these helped me have a happy, positive attitude again. They can help.