Geoff's Miscellany

Socrates was so useful in all circumstances and in all ways, that any observer gifted with ordinary perception can see that nothing was more useful than the companionship of Socrates, and time spent with him in any place and in any circumstances. The very recollection of him in absence brought no small good to his constant companions and followers; for even in his light moods they gained no less from his society than when he was serious. 

(Xenophon's Memorabilia 4.1.1)

I suppose that should one make an effort to be such a man or woman as this, then one would have no shortage of friends.