Do not brood over your past mistakes and failures as this will only fill your mind with grief, regret and depression. Do not repeat them in the future.
SivanandaThe mental ability to concentrate is inherent to all; it is not extraordinary or mysterious. Meditation is not something that a Yogi has to teach you; you already have the ability to shut out thoughts.
SivanandaTo achieve that state of lasting happiness and absolute peace, we must first know how to calm the mind, to concentrate and go beyond the mind. By turning the mind's concentration inward, upon the self, we can deepen that experience of perfect concentration. This is the state of Meditation.
Sivananda