You never know what motivates you.
Only the educated are free.
Leap, and the net will appear.
To know oneself, one should assert oneself.
Begin to be now what you will be hereafter.
It's always too early to quit.
Go for it now. The future is promised to no one.
The secret of getting ahead is getting started.
I can, therefore I am.
Never complain and never explain.
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.