I take away when I shouldn't

Uhh so hi haha well I honestly don't know how to start these things eeh here goes, I deprive myself from fully enjoying my happy moments. Whenever I am feeling happy or laughing or something like that I will have a moment whereby I'll stop because of a thought or a feeling that will tell me that yeah you are laughing now but not forever, yeah you are happy now but tomorrow you will most probably be crying or in pain. It sucks because it's true I'll be happy today but tomorrow I will be crying. It's like I am so used to being sad and depressed that whenever I'm happy I can't fully bring myself to enjoy that feeling with fear of my negative feelings taking over.