Describing the beauty of Eretz Yisroel, G-d says “..a land where rocks are iron…” (Deut 8:9). The Land of Israel has to be populated by people of whom the Talmud says “if a wise man isn’t tough as iron, he can’t be considered a wise man …” The Jewish soul is akin to iron. It can withstand any pressure and can stand up to a test that’s been ongoing for millennia. Its name is Exile.
To topple a strongman
It says in Tanya that to overcome the evil inclination, one needs alacrity.
In order to develop alacrity in the soul, one needs to live joyfully, with an open heart. To accomplish this one needs to cleanse one’s soul of all sadness and preoccupations. If you have succumbed to laziness and heaviness, know that you’re threatened with a condition known as a “stone heart”, this is when a person is unable to be sympathetic to someone else’s misfortune and doesn’t feel the weight of their own problems. This is usually accompanied by sadness. Two people may be engaged in a fight and one of them may be much stronger than the other. However, if the stronger one isn’t light on his feet, he will be defeated.
(From the writings of the Sixth Lubavitcher Rebbe)