Einstein, as we all know, was a truly brilliant man, and as we can see here from this quote, not just in the Physics arena. I think that a lot of times we get these things out of order and a little twisted. If we go on in our lives making the same mistakes over and over, not only are we wasting good sense and time, but we are also not using our most valuable resource, our own choices and memories. We are our own personal history book. If you don't learn from your past, you are doomed to repeat it, plain and simple. Next, there are too many people who don't use the present as they should, they spend it either dwelling on the past, or focusing too much on the future, or what we wish we had. This is a damnable offense, in that the only time we can live in is the present. Focusing too much on what we want in the future is different than hoping for it, hoping for the future means staying positive and planning ahead, making choices today that will help you tomorrow, that's the key.
We should never stop questioning and evaluating ourselves and those around us, what we believe, what we trust. Never be just a sheep, look for answers to your questions, don't take anything at face value, examine it! An inquisitive mind is a useful one!