Joking about mental health illnesses is extremely inconsiderate. Saying stuff like “I want to die” when something goes wrong isn’t ok as you don’t know what it's like to have suicidal thoughts or intentions. Saying stuff like “I’m so triggered” is incorrect, you're angry, you aren’t suffering from PTSD and it hasn’t been triggered. When you say “This is giving me anxiety”, yes you might be scared but the phrase you're looking for is “I’m so anxious”. Telling people to kill themselves can also be triggering and upseting to everyone! In other words only say stuff like that if you have been clinically diagnosed with the disorder as it could be disrespectful to those who have been clinically diagnosed. You don’t know what it’s like to actually have the disorder.
You can always learn from something. If it’s something bad, you’ve learnt not to do it again, how you could improve and how you could handle it better. If it's something good, you’ve learnt what's right and what works.
It's perfectly normal to be sad, it's a normal feeling. Don’t be pressured into feeling happy all the time. The media nowadays makes us think that being happy is normal and any contradicting emotion is bad and you should feel ashamed if you aren’t happy. It's important to have balanced emotions.