Be slow to fall into ...

Be slow to fall into friendship; but when thou art in, continue firm and constant.
 Isocrates

Quotes from the same author

The noblest worship is to make yourself as good and as just as you can.
 Isocrates
I decided that it was not wisdom that enabled poets to write their poetry, but a kind of instinct or inspiration, such as you find in seers and prophets who deliver all their sublime messages without knowing in the least what they mean.
 Isocrates
True knowledge exists in knowing that you know nothing.
 Isocrates
True wisdom comes to each of us when we realize how little we understand about life, ourselves, and the world around us.
 Isocrates
The only true wisdom is in knowing you know nothing.
 Isocrates