True enough. But O Sensei was not just talking about peace of mind or just of a way to personally deal with your circumstances. When talking of peace he was talking about world peace as a goal of Aikido.
And as we all practice Aikido I think we should ask ourselves in what way are we contributing to this goal?
Well said, it is not just about peace of mind ... but you do need peace of mind.
On of Ueshiba's quotes:
"Aikido begins with you. Work on yourself and your appointed task. Everyone has a spirit that can be refined, a body that can be trained in some manner, a suitable path to follow. You are here for no other purpose than to realize your inner divinity and manifest your innate enlightenment. Foster peace in your own life and then apply that to all that you encounter."