What is the meaning for I used to be an adventurer like you.but I took an arrow to the knee?

I looked up on the MineCraft forums about minecraft shutting down but then I saw someone type "I used to be like an adventurer like you but I took an arrow to the knee" and I stayed quiet and my cousin near me started laughing like a freak so can you tell me wht it means

It means you used to be adventurous/daring but then something happened that either made you cautious or hurt you somehow. Because of this you are no longer as adventurous/daring as in the past.

Learned my lesson!

It just means that they used to play hard, but got hurt and can't do it anymore.

You used to sleep around a lot and caught an STD

It's a meme from the Elder Scrolls V: Skyrim.