The Buddha Gotama said,
I do not disparage companionship or friendship - to the contrary, I urge you, seek a traveling companion. But if you cannot find a worthy fellow traveler, right-living and wise, overcoming all dangers, gratified and mindful, then wander alone - like a rhinoceros.
We do not have many rhinoceroses here in Colorado, but it is similar to how any herd animal occasionally lives alone: deer, prairie dogs, even sheep will sometimes live alone as part of their lifecycle, or when there are no more advantages to be gained from the herd: sometimes the herd grows too numerous, or competition becomes too hostile, or in other ways the individual finds more harm than help.
Consort through good will, compassion, appreciation, equanimity, unobstructed by the world, any world, having let go of desire, fear, ignorance - you will be undisturbed when death separates you from your friend. You will have become alone, like a rhinoceros.
When a herd animal sets out alone under the conditions described before, they do not suffer the separation anxiety that they otherwise would.
Some who have set out in Sannyasa, having let go of their attachments to live in solitude actually still live a life concerned with worry for their children, their spouses, and cut off their hair as a tree sheds its leaves in the fall - only to pick up what was let go in the spring. They should, in wandering here and there, seek companions who are matured in the life, right-living and wise, overcoming all dangers. They should travel with these companions gratified and mindful, free and separate - but if such a companion is not to be found, wander free and alone like a rhinoceros.
To be good friends in Sannyasa requires compassion without attachment; otherwise the practice is one of an Ardhangini, and is better suited to the Ashramas of Grihastha or Vanaprastha. Friendship in Sannyasa may be compared to how a herd animal may separate without distress; friendship in Grihastha or Vanaprastha may be compared to how a bonded mating pair (of birds, for example) cannot separate without distress, even in death.
To wander alone like a rhinoceros requires giving up attachment to desire, deceit, thirst, all hypocrisy. Delusion is blown away, with no desires for any of the world, any world - those who wander truly alone, like a Rhinoceros. Turning their back on pleasure and pain, sorrow and joy, they have attained pure equanimity and tranquility. They have abandoned their barriers to awareness, expelled their defilements, destroyed aversion and even desire. They are like fish who avoid a baited hook knowing that there might be a little happiness - followed by distress, and death. They are like the fish who tears the net, like cold ashes for a fire - they wander alone like a Rhinoceros.
Everyone should avoid an evil companion who disregards the goal; don't take a friend as someone who is heedless and desiring. Consort with one who is learned, who maintains the Dharma, who is a true friend. Sanyasis, if you would refrain from adornment, riches, sensual pleasure, flavors, and lies - then also wander alone like a Rhinoceros. If you would renounce violence against all beings in adopting Ahimsa, how could you desire children or spouses? Or any companion? You would wander alone, like a Rhinoceros. There is an allure to society, to companionship - but on the heels of this allure there is pain. Would you not, seeing this inevitable pain, wander alone, like a Rhinoceros?
For some, friendship results in sympathy for the friends - feeling such sympathy, how could you feel compassion? You would, by sympathy, find only distress. You would fail your goals. If you cannot conquer sympathy in Grihastha or Vanaprastha, remember: there is no danger of sympathy for those who wander alone, like a Rhinoceros. Worry and concern, for children and spouse, for sociable friends and companions, grows like bamboo, entwining and entangling. It is better to wander alone than to become entwined and entangled. If in the midst of companions and friends, whether at home or wandering, you are ensnared by attachment, and feel pain when these friends change, or are parted from them (for there is pleasurable fun to be had in the midst of such companions), and you cannot free yourself from this sympathy, value your freedom! Wander alone like a Rhinoceros.
Would a drunkard permit themselves to drink one glass? Would a weightlifter who can only lift a hundred pounds attempt to lift a thousand? It is no use to understand the limits of your strength if you do not use that knowledge. Though you can grow stronger, this does not mean you are already strong.
If you would be content with whatever you get, enduring your troubles without dismay, then wander alone like a Rhinoceros. As an elephant in the Matanga wilds would renounce his herd, as a King would renounce his kingdom, wander alone.
An elephant renounces his herd when he is old, as part of his lifecycle. And a king renounces power earlier than death to help the transition of power. A Sannyasi practices similar renouncement.
Monks, if you have renounced women, if you see a woman, wearing beautiful bracelets of gold, clinking, two to an arm, turn away, wander alone like a Rhinoceros. Remember, if you would renounce society, do not undertake careless social talk. As you would avoid unnecessary pain, avoid unnecessary pleasures that, however sweet and charming, elegant and refined, will bewitch your mind. Remember why you renounced these; understand these as dangers: think, "calamity! cancer! misfortune! disease! An arrow! A dagger! A danger - for me!" Understand your distress, the causes of your distress, and choose instead to wander alone like a Rhinoceros.
Prefer to spend your time strengthening yourself. Learn to suffer the cold and the heat, hunger and thirst, wind and sun, mosquitos and horseflies and snakes - learn to suffer loneliness, rather than suffer unwillingly the distresses of attachment. If you would learn compassion and conquer sympathy, wander alone like a Rhinoceros, like a great elephant who has left his herd to live in the wilds.
Persist in attaining your goal, stay ambitious, firm in effort, steadfast and strong; do not neglect your study and practice, comprehend the danger you presently face, the attachments you already have, and do not endanger yourself further - remain intent on ending the craving, remain intent on becoming strong and wise, mindful, confident and certain, perceptive - like a Rhinoceros wandering alone. This is how you will become like a noble lion, roaring in his Pride. You will be the uncaught fish, like wind passing through a net. You will be clean of the muck you find yourself in now, like a lotus rises from the water.
Pride, here, is a pun (the Buddha was fond of puns, and this pun, however forced, translates the intended double meaning)
Are your friends good friends, or bad friends? Do they help you grow stronger, smarter and more compassionate? Do they hold your interests in mind? Do they help you become who you want to be, and achieve your goals? When you with them, do you feel what they feel, do you feel sympathy - or compassion? or nothing at all? Loneliness is painful, but just as you would avoid poisonous food, or must sometimes do without water, or must sometimes tolerate heat or cold, or mosquitos, you should avoid those false "friends" who would harm you - and if you cannot find those who will help you, associate with those who will at least cause you no harm. Would you listen to sad music when depressed, or prone to depression?
The silence may be unbearable, but at least it causes no harm.