There's a fundamental difference, if you look into the future, between a humanity that is a space-faring civilization, that's out there exploring the stars, compared with one where we are forever confined to Earth until some eventual extinction event.
Look not mournfully into the past, it comes not back again. Wisely improve the present, it is thine. Go forth to meet the shadowy future without fear and with a manly heart.
The secret of health for both mind and body is not to mourn for the past, nor to worry about the future, but to live the present moment wisely and earnestly.
Fate is unalterable only in the sense that given a cause, a certain result must follow, but no cause is inevitable in itself, and man can shape his world if he does not resign himself to ignorance.
Today is thine to spend, but not tomorrow; Counting on morrows breedeth bankrupt sorrow: O squander not this breath that Heaven hath lent thee; Make not too sure another breath to borrow.
Engineers build for the future, not merely for the needs of men but for their dreams as well. Thus, inherently, the engineers work is a fearless optimism that life will go forward, and that the future is worth working for.
All human situations have their inconveniences. We feel those of the present but neither see nor feel those of the future; and hence we often make troublesome changes without amendment, and frequently for the worse.
Tomorrow is the most important thing in life. Comes to us at midnight very clean. It's perfect when it arrives and puts itself in our hands. It hopes we've learned something from yesterday.
And I want to say something to the school children of America who were watching the live coverage of the shuttle's take-off. I know it's hard to understand, but sometimes painful things like this happen. It's all part of the process of exploration and discovery. It's all part of taking a chance and expanding man's horizons. The future doesn't belong to the fainthearted; it belongs to the brave. The Challenger crew was pulling us into the future, and we'll continue to follow them.