Something about talking about the “things you are going to do” seems to diminish those very things. Talking about future plans, steals energy from those very plans
The same holds true for things you have already done. Real accomplishment can have its luster worn away by constant recounting.
However, knowing that you are going to do something, and not talking about it has a power that is hard to describe. It puts you one up like a poker player with pocket kings.

Also

Not touting your past accomplishments has that same power. Even better, pocket aces, and most likely to be tuned over by someone else, when they get curious enough.