Your anger, frustration and despair come mostly through the gates of your expectations. Expectation is dependence. True, we have to depend, but if that leads to too many expectations then inevitably you are heading for misery. Meditation and mindful-living helps you to develop that inner power by which you gradually strengthen your muscles of self-dependence. Invariably, you are no more at the mercy of others. You are at the mercy of only God in you!
Love and light!