Eknath Easwaran said this quote

But when we train the senses we conserve our vital energy, the very stuff of life. Patient and secure within, we do not have to look to externals for satisfaction. No matter what happens outside--whether events are for or against us, however people behave towards us, whether we get what pleases us or do not--we are in no way dependent. Then it is that we can give freely to others; then it is that we can love.