(verb) (defective) To use caution, pay attention to (used both with and without of).
"The first step of healing is to beware of your own negative thoughts."
"Cherish those who seek the truth but beware of those who find it."
"Beware the barrenness of a busy life."
"I say, beware of all enterprises that require new clothes, and not rather a new wearer of clothes."
"Beware of false knowledge; it is more dangerous than ignorance."
"Beware of little expenses; a small leak will sink a great ship."