The number of things that are actually under our control are surprisingly few.
"Only you can prevent forest fires" says Smokey. The reality is that most forest fires are caused by lightning or other naturally occurring events, and we are unable to stop them from happening. And truth be told... Naturally occurring fires are important to the natural cycle of life in nature. Ironically, the more we interfere trying to prevent forest fires, the more overdue the cleansing fires become and the worst the inevitable becomes.
You cannot prevent cancer or any other disease. It seems that every day something new causes cancer and new deadly viruses are born. Bacteria is now more resistant to anti-biotics in part because of how aggressively (and obsessively) we have tried to defeat germs.
You cannot prevent floods or tidal waves or drought or war or famine or homelessness or racism or stupidity.
You cannot prevent global warming or cooling.
You cannot prevent huge geothermal events or extraterrestrial objects from crashing into the Earth.
You cannot prevent your kids from getting in trouble. You cannot prevent them from getting hurt. You cannot prevent them from marrying someone of whom you do not approve.
You can not keep from getting old. You will eventually die.
All you really control is how you live your life and how you react to all these things that are out of your control. You can control how you treat people and for the most part how you choose to spend your time and energy.
Obviously, you can try to influence things. You can eat right and stay away from unhealthy situations. You can raise your children the best you can so they are less likely to have problems. You can help out less fortunate people.
But you can not control these things.
Just accept that fact and you will probably be better off.