Re: 2 people in 6 months dying from sudden death that I know - I can't cope
It is absolutely impossible to die without a reason and although hard to define the biological definition of death is currently brain stem death and clinical the ceasing of heartbeat. Sudden death, often thought to be a result of a cardiac event, is therefore very very likely to be a result of an underlying heart condition and if you are really worrying yourself out of your mind ask your doctor for an ECG as this almost always guarantees that heart problems are ruled out.
Death is a complicated thing that no one really understands at present so don't be too down on yourself for being scared. Take some time to be patient with yourself and you will come to accept it more as you get older, as everyone does. Try searching on youtube for how to accept death and illness. Lots of good videos that might help.
Also understanding probability theory helps. Everyone's probability of sudden death is very very low, but equal. The fact that two people you know has died of it (allegedly, but as you said you don't know the cause of one doesn't mean the cause is sudden death in an otherwise healthy person) doesn't mean you or anyone else are any more likely to die from sudden death.
For example, there are plane crashes, but taking more planes does not make you any more likely to die in a plane crash. It resets each time. This is why gamblers loose lots of money haha, they think there's some sort of link between each, say roll of the die, but I'm actuality each event is independent.
I will confidently bet a million times you wont die in this way.
Take care.
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"The only way out is through." - Robert Frost