I'm with you and completely understand. Mortality is a difficult thing to face. My rational mind knows that even at 42, my risk rate is still low, but the irrational mind says OMG CANCER, HEART ATTACK, STROKE.
But I also work with statistics (ironically a person with HA has to deal with death statistics). Even though cancer is the leading cause of death from 35 to 54, the rates are relatively low. Especially under 44. Death is most likely to happen after age 65. That's why death before 65 is considered premature because you are not expected to die. But the highest rate of death is still after age 85!
I'm 42 and only four people my age who got cancer who were my age. And only one was a close friend. Two died but they were exceptions not the rule, My close friend had breast cancer and it's most likely genetics because her mother got it also at a young age.
Try not to worry about it. Continue doing prescreening. Yearly exam and mammogram, love your children and take it one day at a time.