How much money is enough for a lifetime?

We soon shall see the very first person to become Trillionaire. Currently, there are a few people who have several hundreds of billions of dollars. All of them are either old or soon to be old. Which simply means that they money they obtained and the money they are going to obtain are not for the spending of their own lifetime at this point. Idk, but I believe, at least for some, it might be like getting a high score in a game. Score matters absolutely nothing for them, but they still want to score the highest.

How much money do you believe would be enough for a general person to lead a life he or she won't regret?