the grandmother is significantly older than everyone else, it is possible she sustained those injuries simply because she was older and had weaker skin. this could be an answer, but this is just my train of thought. hope this !
the first step- realize what is causing you stress
symptoms of stress- lashing out for reasons sometimes you don't even know. can't relax muscles. sometimes you can't eat or you eat a lot. you throw up from stress.
ways to control stress-
1. find out what is stressing you out
2. remove yourself away from situation if possible
3. count down from 30 repeat as necessary
5. go somewhere you can scream
6. do something you like to do
7. go for a run
8. cuddle up with animal and read or watch tv