A paragraph on friendship

Please read through the paragraph and make corrections where you find mistakes. Also, please help me sum up the paragraph well. I tried it but I couldn't get a better ending sentence. I don't like the one I wrote. Thanks.

Friendship is a relationship of mutual affection between two or more people. Trust, sharing, caring and being supportive to one another are the basic characteristics of friendship. Age, caste, beliefs, religion, etc nothing matters in friendship except sincerity and honesty. It is the cause of feeling happiness for the success and sadness for the melancholy of friends. It last for lifetime even if friends are not in touch. In short, it is the most valuable relationship in a person's life.