I don't believe there's anything in life you can't go back and fix. The ancient Vedas - the oldest Hindu philosophy - and modern science agree that time is an illusion. If that's true, there's no such thing as a past or a future - it's all one huge now. So what you fix now affects the past and the future.
In Philosophy, the contemplations of man do either penetrate unto God, or are circumferred to Nature, or are reflected and reverted upon himself. Out of which several inquiries there do arise three knowledges, Divine Philosophy, Natural Philosophy, and Human Philosophy or Humanity. For all things are marked and stamped with this triple character of the power of God, the difference of Nature and the use of Man.
Again men have been kept back as by a kind of enchantment from progress in science by reverence for antiquity, by the authority of men counted great in philosophy, and then by general consent.
'Twas strange that one so young should thus concern His brain about the action of the sky; If you think 'twas philosophy that this did, I can't help thinking puberty assisted.
...But nature does not say that cats are more valuable than mice; nature makes no remark on the subject. She does not even say that the cat is enviable or the mouse pitiable. We think the cat superior because we have (or most of us have) a particular philosophy to the effect that life is better than death. But if the mouse were a German pessimist mouse, he might not think that the cat had beaten him at all. He might think he had beaten the cat by getting to the grave first.
Every age must look for its sanction to its poetry and philosophy, for in these the human mind, as it looks backward or forward, attains to an eternal state.