I,personally, agree with this statement. Even if books nor other people say that it's bad to boast, they too experienced these things. I mean, faced it. This is really reality. But even though this is reality and everyone did experienced this kinds of these, we can change that fact. If you're rich then stay silent. Being rich doesnt even mean that you can rule the world nor does it mean that you are more powerful than those average type of people because actually, we are all people. No one should be treated differently.
In fact, we should be treated equally no matter what our status in life is. Being poor doesnt also mean that you're the lowest life form on earth. No one is. You just need perseverance and hard work to overcome it. Don't grumble since it wont do good in your life, rather, it could make your life worst since you think life is hard because you don't have enough money. Money isnt the answer to everything. Love is something that can make your life happier than money. Even if we need money, we shouldnt go to the extent in stealing it or cheating to win it. Be contented because when we are gone in this world, no matter how rich you are, without happiness or love, you can't live a fulfilled life. Your riches even won't go with you when you die so just live life simply yet to the fullest.
HOPE THIS HELPS! :)