How you play a game predicts how you handle real life.

Resources, exploration, formulating a plan, meeting objectives, identifying goals / milestones, keeping score, etc.

They have their parallels in real life and it's difficult to override your tendencies to do things a certain way.

For example, if you tend to think before you leap, you are less likely to do YOLO things in-game.

If you are an explorer type, you are more likely to go off the beaten path and look for side quests and interesting locations in a game.

If you like to keep updated and current when it comes to consumer goods and electronics, you are more likely to spend your in-game currency as soon as you get enough to acquire that shiny new weapon / armor.

This isn't to say that watching you play a game will allow me to have a complete picture of who you are.

Because context, companions, and frame of mind have to be taken into consideration as well.

But it can give a rough idea of your likes, dislikes, and tendencies. And that's always useful if we have to face off or interact in the virtual world.