I think one of my most detested pieces of "advice" is when someone says, "just look on the bright side!" Or "think positively!"
Not only can that be really dismissive of your feelings and invalidating of your experience, especially with mental illness, but genuinely harmful. I'm not sure if that's advice you're trying to live out or something you are trying to reach on your own, but I would encourage you to maybe set a different goal.
"Happy" isn't the default state of humans, in fact no emotion is our default. Emotions are like weather, something always has to be happening. Somedays are cloudy, some are sunny, some are blizzards that dump a couple feet of snow and you're stuck at home. Sure it's a good goal to work for more sunny days and fewer blizzards, but the weather always shifts and everyday can't be blue skys and sunshine. Nor should it be! As a human, it's okay to experience sadness, especially when things don't go your way. It's part of the human condition.
I'm sorry you've had a rough couple days. That's never fun and always so frustrating. My advice is to allow yourself to feel those feelings. Accept that it's okay to be frustrated and sad when things don't work out. Try not to dwell on those feelings, but feel them as long as they demand to be felt. Then let go, look forward, and find joy in other things. Just like the weather, know that it will always change and eventually, it will be sunny again.
Much easier said than done, I understand, but that is what I try to do and honestly, I only started really having problems with it when people tried to get me to "just be positive". Now I'm finding my way back 😊