A famous quote says “No matter what condition you are in, think of something good”.
This is not always easy to do when you are in a low place, but it will definitely help.
Relive that moment. Feel what you felt then. Make your memories pull in everything about that time.
Be glad and appreciative that you have a life with those great times.
Picture future events that make you happy. Expect more great times to come.
As you do this, you will find your spirits lifted.
Also, smile. These 2 exercises will make all the difference!