1. You cannot really know 'what might have been' so it is meaningless and unfair to measure what you have or where you are against a fiction, a great maybe, a ghost.
2. The value of what you chose comes from its being chosen. To say that it is the 'right choice', that is, to explain away why it was chosen, can only come after--a great rationalisation, a hopeless excuse, but a necessary testimony which only has value to you and no one else.
3. A mistake is just that: mis-taking a choice for what is 'correct' or 'right' only to find out it was not what you thought it to be. But objectively, things and choices are indifferent; they are just there, neither right nor wrong, neither good nor evil. It is us who give value to them prematurely. Thus to be mistaken is to assume too much, hope too much, want too much. A man can never be mistaken if he just let things be what they are without asking more from them.
4. "Man has no excuse." He can neither complain nor regret what he has and what has befallen him. Strictly speaking, you can always kill yourself. To continue living assumes you accept everything that happens to you, that you decide to carry the burden which naturally comes with living a life.
5. I have learned that in order to live peacefully, you just have to let things decide for themselves. And that wisdom comes not in calculating possibilities, having courage in deciding, but in discerning the direction to which reality points, feeling instead of thinking. Some call this God's gentle persuasion. I have lost admiration in those who always think things through. Greater are the poets of living.