@Moon @arzachel @jeffcliff german study on that topic:

https://herzstiftung.de/ihre-herzgesundheit/coronavirus/myokarditis-nach-corona-impfung

key facts from the study:
854 Patients between 12-20 years old

average day of symptoms was 2.6 days

"most" people had to go to the hospital

1/4 of the patients went to the ICU (they had a rhythm issue with their heart and it is apparently normal practice to go to the icu than in case it gets suddenly worse)

none died

on average after 3 days they could leave

long term (6 months) they compared 102 youth patients with vaccine associated myocarditis to youth 762 patients with corona associated myocarditis.

1 of the youth patients died after vaccine associated myocarditis
84 of the corona associated myocarditis

so it is 1% to 11%. that said the cause of death wasnt included in the study.

so i guess the qualitative damage of myocarditis is very different if it is because of corona or the vaccine. also there are good reasons for the usual precautions one should take when getting a vaccine: dont be sick, no alcohol, no sports, etc...