As Shakespeare had Hamlet say, “There is nothing either good or bad, but thinking makes it so.”
So that’s the first objection that I have to what you wrote. “Good” or “bad” are attributes that you can assign depending on how you think.
After that, even if bad things do happen to positive people, they can make the best of it.
“It’s an ill wind that blows nobody any good.” I wish I could recall who said that, because it’s pretty apt. For a literal example, hurricanes, though they do widespread damage, also bring much-needed rain to some places.
Finally, consider the story of the twin brothers, one an eternal pessimist and the other a perfect optimist. Their parents gave them different Christmas presents: To the pessimist they gave a beautiful Arabian horse. The optimist received a stall in a barn filled with horse shit.
When the boys awoke on Christmas morning, they had different reactions to their gifts. The pessimist was thinking of how much he’d have to work to take care of his beautiful horse, all the training and exercise and feeding he’d have to do, and the vet bills he’d have to pay in the future. He was not at all pleased with his gift.
The other boy, though, was excited as he cheerfully started mucking out his stable, grinning from ear to ear and whistling as he shoveled all the shit out of the barn. “With all this shit, there’s got to be a pony in here!” he said as he went back to work.