Either you run the day or the day runs you.
Well done is better than well said.
I can, therefore I am.
Go for it now. The future is promised to no one.
Leap, and the net will appear.
Only the educated are free.
By failing to prepare, you are preparing to fail.
To know oneself, one should assert oneself.
Be kind whenever possible. It is always possible.
Be gentle to all and stern with yourself.
In hard-core science fiction in which characters are responding to a change in environment, caused by nature or the universe or technology, what readers want to see is how people cope, and so the character are present to cope, or fail to cope.