When i was really young, like around 5 we had 2 goldfish in a bowl. They lasted a few years from what i recall.
My first real tank of my own was when i was around 10, small one that i kept an axolotl in, i really looked after it and even had a worm farm so i could feed him his daily earthworm. It got big and 2 years later my parents got me a 2 foot tank so i could upgrade. Sadly i didnt know much back then and just filled it up and dropped him in. changed its diet to sliced up beef heart as it was summer and worms were harder to come by and a week later he was dead and i was heartbroken. I still feel bad now recalling it all, the thought that the new tank would be great for it and how excited i was and then the death of a pet.
I learned a harsh lesson that good intentions can sometimes have a bad outcome, it took me a good few years to learn about cycling tanks etc. when i did i realised what a mistake i had made and how easy it could have been prevented.