They all suggest to live your days with focus on your current opportunities, to be present-oriented, and take advantages of what you have now to succeed. Do not wait, because you may loose a great chance! You cannot go back and change your past, but you can work on your present and future.
Certain opportunities only come once in your lifetime, so, do not waste your day in ruminating. DO IT and do it well.
I hope it helps. :)