We all have gone through this absurd feeling. It is an integral part of our life. Nobody can explain it. Its called one sided love.
You may have known that person for a long time, or you may have just met her, but suddenly you'll realize, "Gosh I am in love". Its the simplest and most enduring feeling in the world. You will feel as if the whole universe is at your feet, your confidence will be touching the Himalayas and you will feel like you can break a sharks tooth with your bare hands.
You start to think about that person all the time, suddenly all the things about her becomes amazing and charming. You start to laugh at her silly jokes. apparently your observation skills obtain superhuman qualities and you notice the tiniest of things like butterfly shaped earrings, roman chappals, eyeliners etc (all things which were oblivious to your eyes till then). You will go into the stealth mode and try to find ways to smell her hair without letting her know about it. You will be waiting for her phone call and if it doesn't come then you will find all the stupid excuses to call her like, "Hi, do you know which came first, an egg or the chicken ?"
The next phase is the "J" word, alias jealousy. When she will say that my best friend is Ramanujam swamy (trust me, even a name like Hrithik will sound like that at that time), you'll feel like killing, no no not yourself but that swamy person.
You will not tolerate any other person speaking, listening, walking, eating, dancing with her at all.Once she notices that you are smitten by her charm, she will start her own little thingie.She will talk to you, listen to you and be your friend. She will also make you carry her bag, buy her drinks, make food for her. She will order you to do things in front of her friends and you will be feeling wow she is flaunting me in front of them.
Then one day when you go and tell that you like her, she will look into your eyes and say, "you are my very good friend, but I can never see us in a relationship. Lets just be friends" in other words, you can still be my dog and do all the things which I ask you to do.
If you have any self respect, you will feel dizzy and as if somebody has punched you hard in the stomach.
Suddenly you will have the worst headache of your life. You will feel cheated and used. You will try to cry but you will not be able to. Then you will try to remember all the bad things that have happened to you in your life and generate that tiny drop which will (with luck) turn into a tidal wave of cry.
Trust me, nothing is more relieving than crying your sorrow out. You'll feel light and in god mode.
The phase over and out mode - You will try to forget her but it will not be that easy, you will avoid meeting her and your common friends, you will try not to go to the places visited earlier and you will delete all her photos from facebook, orkut and your mobile phone.
It may take a minimum of 10 days to years to forget that person; actually it depends on your luck. But to appreciate a relationship this thing is important, because you may have also knowingly or unknowingly done the same thing to somebody else.