I did a reasonably good job at timing Nvidia stock. I bought three shares in February of last year, and it's more than tripled since then. Initially I was really happy to have bought when I did, but almost as quickly I started thinking "damn, if I had bought ten shares..." or "if I had bought an option contract instead..." as if me making two grand wasn't objectively a great thing.
It's not rational, but I think it must just be instinct to always want "more", no matter how silly it becomes. It seems like the first thing people want when they have a billion dollars is a second billion dollars.