Green things

How is it possible for a person who can keep any green plant alive kill every cactus they've ever owned?

The garden is suffering a bit right now too. It's just too hot and where the garden is (the only place it can go) gets the hot afternoon sun. The bugs are insane here also and it's hard to keep the plants free of them. Tomatos are on the vine already though. Looking yummy. It's just so hot and miserable. I don't think i can ever get used to it being hot in the morning and through the night. I miss cool nights and mornings. I really want to walk outside but it's just way too hot any time of the day.