One should experience the positive and negative sides of life.
No life without Sun
A friend is the one who comes in to your life either during a good celebration or at our bad moment of live and stays with us for ever since then. where as a enemy is one who would leave from our life for his own mistakes and undermining our capability and ability.
A friend is one who knows all about you, and still likes you. A enemy is one who talks all about you negatively with others and wont like you.
A real friend is one who would spend on you unmindful of results and return gestures from your side. A enemy is one who would be interested benefits from your end only and he never spends for you.
A real friend is one who gives his helping hand and be with us in good and bad times. A real enemy is one who will be with you in good times and shy away during your bad times.
'Idhuvum Kadandhu Pogum "
Even this challenging situation would ease
We do talk of friends, good friends and best friends and we also talk of enemies and sworn enemies but what I feel is that friendship or enmity depends a lot on situations that keep changing in one's life. It is a bit difficult to honestly and strictly categorize people into friends or enemies because humans are susceptible to changes and such changes are quite unpredictable. One who is a friend today may become your enemy tomorrow and vice-versa.
But if I am to draw a difference between the two, I would put it that a friend is one who understand and accept us wholeheartedly as what we are and would stand by us in the worst situations and assure us that we can fall back on him; while an enemy is one who is not so otherwise but would be so based on certain conditions that suits him and would be framed by him and is not at all reliable. To add on, a friend may never harm you but an enemy won't think twice before inflicting an harm on you if it suits his interests.
'Real knowledge is to know the extent of one's ignorance'- Confucius
But enemies are temporary. When we are in schooling there will be a competition between students. Rank 1 and Rank 2 will have lot of competition. They will envy each other. But this is a temporary phase. He may become your best friend also.
I always feel friendship should be permanent and enmity should be temporary.
One should be careful about choosing his friends. A wise enemy is always better than foolish friend.
There are some people who pretends to be your friend but behind you they may be doing bad for you. So we should always judge our friends and act. A good example for this is Duryodhan's friendship with Sakuni. Sakuni acted as friend of Duryodhana and make sure that Duryodhana will loose everything in his life.
So be attentive in making friendship and make it permanent.
It is the learning process in language when we come to know about enemy, when we start learning similar and opposites etc. But as kids we would not have enemies, we may feel about them as 'bad friends'.
It is only after w become adults and have something at stake that we come to treat some people as enemies. Then it proceeds to a stage that mutual friendship become based not on love and affection, but on enmity -- enemy of my enemy is my friend.
The world now functions that way. Friends and enemies can also be contextual or situational.