Study requires solitude, and ...

Study requires solitude, and solitude is a state dangerous to those who are too much accustomed to sink into themselves
Study requires solitude, and solitude is a state dangerous to those who are too much accustomed to sink into themselves

Quotes from the same author

If a man does not make new acquaintances as he advances through life, he will soon find himself left alone. A man, sir, should keep his friendship in a constant repair.
To keep your secret is wisdom; but to expect others to keep it is folly.
Love is the wisdom of the fool and the folly of the wise.
Memory is the mother of all wisdom.
Friendship, like love, is destroyed by long absence, though it may be increased by short intermissions.