Good luck Omega,
We're thinking about your sister and your family.
Trust me Matthew, aside from the few moments when my mind manifests the bad possibilities (which isn't often), I'm relatively calm and collected, if not almost too calm. People tend to think I'm high because I am so calm most of the time.
It's totally ok. We all deal with stress differently. Being calm and collected helps those around you more than you think.
Hang in there. Life tests us all the time. Especially when you least expect it.