Be gentle to all and stern with yourself.
Be kind whenever possible. It is always possible.
Be thine own palace, or the world's thy jail.
What you do today can improve all your tomorrows.
Expect problems and eat them for breakfast.
After a storm comes a calm.
If you've got a talent, protect it.
Always desire to learn something useful.
The secret of getting ahead is getting started.
If you think you can do it, you can.
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.